What are the safety management requirements for temporary electricity use at construction sites?
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I am seeking advice from everyone regarding the safety management systems, regulations, or required documents for temporary electricity use at construction sites
It is recommended to refer to the following two standards: GB50194-1993 Code for Safety of Power Supply and Use at Construction Sites, and JGJ 46-2005 Technical Code for Safety of Temporary Power Supply at Construction Sites
You can also refer to GB 3883.1-2008 Safety of hand-held electric tools – Part 1: General requirements
Code for Safety of Power Supply and Use at Construction Sites GB50194-1993 1 General Provisions 1.0.1 This code is formulated to implement the principle of \"safety first, prevention first\" in power supply and use at construction sites, to ensure the safety of personnel and equipment during such operations, and to guarantee that the design, construction, operation, and maintenance of power supply and use facilities at construction sites are safe and reliable, as well as of high quality and economically sound. 1.0.2 These specifications apply to the design, construction, operation, and maintenance of power supply and consumption facilities at construction sites for general industrial and civil construction projects, where the voltage is 10 kV or less. However, it is not suitable for special applications such as underwater, underground, and mine environments. 1.0.3 To ensure the safety and reliability of power supply and utilization at construction sites, in addition to complying with these specifications, it is also necessary to adhere to the provisions of **current relevant standards and specifications. 2 Power generation facilities, substation facilities, distribution facilities 2.1 Power generation facilities 2.1.1 At construction sites that are far from power sources or where the available power sources are insufficient, power generation facilities such as diesel generators and train power stations can be installed. 2.1.2 The site selection for power generation stations shall meet the following requirements: 2.1.2.1 Be located near load centers. 2.1.2.2 Convenient transportation and route access. 2.1.2.3 Located downwind of the wind direction with the lowest annual frequency at the pollution source. 2.1.2.4 Stay away from construction hazard areas. 2.1.3 The layout within the power plant area shall meet the following requirements: 2.1.3.1 Buildings should be as compact as possible, in line with the production and operation procedures. 2.1.3.2 The generator room is located within the station area, on the upwind side of the wind direction corresponding to the lowest frequency throughout the year ； The control room and power distribution room are located on the downwind side of the machine room. 2.1.3.3 The cooling ponds and spray ponds shall be located on the upwind side of the machine room and outdoor power distribution equipment, with respect to the wind direction at the minimum frequency in winter. 2.1.3.4 The slope of the floor drainage within the station shall not be less than 0.5%. 2.1.4 Fuel tanks should preferably be steel tanks, and their number should not be less than 2. 2.1.5 The accident oil sump should be located outside the generator room, with a distance of not less than 5m from the outer wall of the generator room. The fuel storage capacity of the accident oil tank should not be less than the total amount of fuel required for daily use. 2.1.6 Diesel engines shall have separate exhaust pipes and silencers ； The smoke exhaust pipes installed overhead in the generator room should be equipped with insulation layers. Fire prevention measures should be taken when the smoke exhaust pipe in the gutter passes through the oil pipeline. The distance between the vertically installed smoke exhaust duct outside the generator room and the generator room itself must be no less than 1 m ； The outlet of the smoke exhaust pipe should be above the roof edge, with a height of not less than 1 m. 2.1.7 The location where mobile diesel generators are parked should be level, and it is advisable to raise it 0.25–0.3 m above the surrounding ground. The front and rear wheels of the diesel generator trailer should be secured. 2.1.8 The trailer of a mobile diesel generator shall have a reliable grounding. 2.1.9 A rain shelter should be provided on the upper part of the mobile diesel generator trailer. The rain shelter should be sturdy and reliable. 2.1.10 Stoves and blowtorches shall not be used within 4 meters of mobile diesel generators, nor shall flammable materials be stored there. 2.1.11 The total capacity of the diesel generators shall meet the requirements of the maximum load as well as those arising from the starting of large-capacity motors. The bus voltage at startup should not be lower than 80% of the rated voltage. 2.1.12 Diesel generators operating in parallel shall be equipped with synchronization devices. 2.1.13 The outlet side of the diesel generator shall be equipped with devices such as short-circuit protection, overload protection, and low-voltage protection. 2.1.14 Fire-fighting equipment suitable for use in live areas shall be installed within the power plant, and it shall be placed in locations where it is easily accessible. 2.2 Substation and distribution facilities 2.2.1 The location selection for substations and distribution stations shall meet the following requirements: 2.2.1.1 Be located near power sources and have convenient transportation access. 2.2.1.2 Proximity to the load center facilitates the introduction and exit of lines. 2.2.1.3 The area shall not be flooded or accumulate water, and the ground drainage slope shall be not less than 0.5%. 2.2.1.4 It should be located on the downwind side of the wind direction with the lowest annual frequency at the pollution source, and away from areas prone to fire and explosion as well as locations with severe vibrations. 2.2.2 The buildings for the transformer room, control room, and distribution room shall meet the following requirements: 2.2.2.1 Protection against rain and wind sand ； The fire protection rating shall be no lower than level 3, with the transformer room requiring a rating of no lower than level 2. 2.2.2.2 Use louvered screens or window metal meshes, with mesh openings not exceeding 10mm×10mm. 2.2.2.3 The lower edge of the high windows providing lighting from adjacent streets shall be at a height of not less than 1.8m above the outdoor ground level. 2.2.2.4 The door opens outward, and its height and width are suitable for the entry and exit of equipment. 2.2.2.5 The area and height shall satisfy the safety distances required for the maintenance and operation of the distribution equipment, and comply with the provisions of **current relevant standards. 2.2.3 Transformers with a capacity of 400 kVA and below can be installed on poles. The bottom of the pole-mounted transformer should be at a height of not less than 2.5 m above the ground. 2.2.4 Transformers with a capacity of 400 kVA or more should be installed on the ground. The platform on which the transformer is installed should be 0.5 m above the ground level, and it should be surrounded by a fence with a height of not less than 1.7 m. The distance between the fence and the outer perimeter of the transformer must be no less than 1 m, and a warning sign should be hung in a prominent position on it. 2.2.5 High-voltage and low-voltage fuses shall be installed on the high-voltage side and low-voltage side of the outdoor substation transformer respectively ； The vertical distance from the ground to the fuse should be no less than 4.5 meters for high-voltage systems, and no less than 3.5 meters for low-voltage systems. The horizontal distance between phase fuses should be no less than 0.5 m for high voltage and no less than 0.3 m for low voltage. 2.2.6 For transformer substations located among trees on the sidewalk, under maximum wind deflection conditions, the minimum distance between the live parts and the tree tops should be no less than 2 meters for high-voltage systems and no less than 1 meter for low-voltage systems. 2.2.7 When connecting the transformer leads to cables, neither the cables nor their terminals shall come into direct contact with the transformer enclosure. 2.2.8 When powered by a box-type substation, its enclosure shall have reliable protective grounding. The grounding system shall meet the product’s technical requirements ； The door of the box, which contains instruments and relays, must be securely connected to the housing. 2.2.9 After the box-type substation is installed or after maintenance, electrical equipment inside it shall be inspected and subjected to electrical performance tests before it can be put into operation; it may only be operated once these tests are successful. 3 Imaginary power distribution lines and cable lines 3.1 Selection and installation of utility poles 3.1.1 Reinforced concrete poles are preferred for utility poles. Reinforced concrete utility poles must not have exposed rebar, nor shall they exhibit defects such as circumferential cracks or twisting. If wooden poles and crossbars are used, their material must be sturdy, free from decay, splitting, and other damages. The total length of the wooden pole should not be less than 8 m, and its diameter should not be less than 140 mm. 3.1.2 The burial of utility poles shall meet the following requirements: 3.1.2.1 There shall be no tilting, sinking, or water accumulation at the base of the pole; if these conditions are not met, a base plate or clamp should be used. 3.1.2.2 When backfilling, the soil clumps should be broken up, and the soil should be compacted once for every 0.5m of backfill. The pole pit should be equipped with a anti-settlement platform, whose height should exceed the ground level by 0.3 m. 3.1.2.3 The burial depth of utility poles shall meet the design requirements; in the absence of such requirements, it shall conform to the provisions in Table 3.1.2. Burial depth of utility poles (m) Table 3.1.2 Pole height: 8.0, 9.0, 10, 11, 12, 13; Burial depth: 1.5, 1.6, 1.7, 1.8, 1.9, 2.0. Note: Special measures should be taken in cases of soft soil, quicksand, or high groundwater levels. 3.1.2.4 In extremely cold regions, it should be buried below the permafrost layer. 3.1.2.5 The burial depth of poles equipped with transformers should not be less than 2m. 3.1.3 The burial of tension cables shall meet the following requirements: 3.1.3.1 The depth of the trench for the tension cables should be 1.2 to 1.5 meters. 3.1.3.2 The angle between the tension cable and the telegraph pole should not be less than 45°; when constrained by terrain, it shall not be less than 30°. 3.1.3.3 The guy wires of the terminal poles and the tensioning pole guy wires should be aligned in the same direction as the line ； The angle-dividing cable and the line’s angle-dividing direction should be aligned ； The wind-resistant tie wire should be perpendicular to the direction of the line. 3.1.3.4 When a tie rod passes between conductors, a tie rod insulator shall be installed. The height of the pull-line insulator above the ground should not be less than 2.5 m. 3.2 Line Installation 3.2.1 The route of the power supply lines should be chosen carefully; it is necessary to avoid areas that are prone to collisions, damage, erosion by rainwater, and corrosion by gases. Additionally, such routes should stay away from thermal pipelines, rivers, and areas with heavy traffic during construction. 3.2.2 Insulated wires shall be used for low-voltage overhead lines at construction sites in areas with frequent human activity or where large machinery is operated. Insulated wires shall not be laid overhead in bundles, nor shall they be directly tied to utility poles, trees, or scaffolding, nor dragged across the ground ； When laid underground, it must be placed in a pipe; there must be no joints inside the pipe, and its ends must be sealed. 3.2.3 The selection of the conductor cross-section shall meet the following requirements: 3.2.3.1 The load current in the conductor shall not exceed the allowable current-carrying capacity of the conductor. 3.2.3.2 The allowable voltage drop at the end of the line shall not exceed 5% of the rated value. 3.2.3.3 When the conductor crosses railways, highways, or other power lines, the cross-sectional area of the copper stranded wire must be no less than 16 mm2 ； The cross-sectional area of aluminum conductor with steel core shall not be less than 25 mm2 ； The aluminum stranded wire shall not be less than 35mm2. 3.2.4 When lines intersect, the minimum vertical distance between the conductors of different lines shall comply with the requirements specified in Table 3.2.4. Minimum vertical distance between conductors at line intersections (m) Table 3.2.4 3.2.5 The minimum distance between line conductors and the ground shall meet the requirements specified in Table 3.2.5 under the condition of maximum sag. The minimum distance (in meters) between the conductor and the ground at the maximum sag is given in Table 3.2.4. 3.2.6 The minimum distance between the line conductors and any protruding parts of buildings at the maximum sag and under maximum wind deflection must comply with the requirements specified in Table 3.2.6. Minimum distance (m) between conductors and protruding parts of buildings Table 3.2.6 3.2.7 When several circuits are installed on the same pole at a construction site, high-voltage circuits must be located above low-voltage circuits ； Power lines must be located above communication lines ； The minimum vertical distance between the crossarms of lines installed on the same pole shall meet the values specified in Table 3.2.7. Minimum vertical distance (m) between crossarms of lines installed on the same pole Table 3.2.7 Note: For corner or branch lines that are single-circuit, the distance between the crossarm of such branch lines and that of the main line is 0.6 m ； In the case of a double-circuit configuration, the distance between the crossarm of the branch line and the upper main line crossarm is 0.45 m, while the distance to the lower main line crossarm is 0.6 m. 3.2.8 The sag of the line at different spans shall comply with the provisions of the installation curves for 10 kV and lower overhead lines in the **current standards. 3.2.9 Within the same span, a conductor shall have no more than 1 joint ； There should be no more than 2 joints per span on the same line. 3.2.10 There shall be no joints where overhead lines cross highways, railways or other power lines, as well as internal factory roads. 3.3 Cable Laying 3.3.1 Power supply cables should be buried along the roadside or the edge of buildings, and it is advisable to lay them in a straight line ； Cable direction markers should be installed every 20 meters at turns and along straight sections. 3.3.2 When cables are buried directly in the ground, the distance between their surface and the ground level should not be less than 0.2～0.7m ； Soft soil or sand should be laid above and below the cable, with a thickness of not less than 100 mm, and it should be covered with bricks for protection. 3.3.3 At the intersections of cables with railways and plant roads, they shall be laid in sturdy protective pipes ； Both ends of the pipe should extend 2m beyond the roadbed. 3.3.4 When low-voltage cables (excluding oil-immersed cables) are to be installed overhead, they should be routed along buildings and structures, with the installation height not being less than 2 m ； The joints should be well insulated, and waterproof measures should be taken. 3.3.5 When cables are buried directly in the ground, the minimum distances between cables, as well as between cables and other pipelines, roads, buildings, etc., in parallel or at intersections, shall comply with the requirements specified in Table 3.3.5. It is strictly prohibited to lay cables parallel above or below the pipeline. Special cases shall be handled in accordance with the following provisions ； 3.3.5.1 In the areas between power cables and control cables, as well as within 1 m in front of and behind their intersection points, if the cables are placed inside tubes or separated by partitions, the required crossing distance can be reduced to 0.25 m. 3.3.5.2 When cables run parallel to or intersect with thermal pipelines (trenches) and thermal equipment, insulation measures shall be taken to ensure that the temperature rise of the soil surrounding the cables does not exceed 10°C. 3.3.5.3 Where the distance between cables and thermal pipelines (in trenches), oil pipelines (in trenches), pipelines for flammable gases and liquids (in trenches), thermal equipment or other pipelines (in trenches) meets the required standards, but maintenance of these pipelines may cause damage to the cables, protective measures shall still be taken within a range of 1 meter before and after the intersection points ； When the cross-distance does not meet the requirements, the cable should be inserted into a tube, reducing the distance to 0.25 m. Minimum distances between cables, as well as between cables and pipes, roads, and buildings, in parallel or at intersections. Table 3.3.5 3.3.6 The openings of cable trenches or cable ducts that lead into substations and distribution stations should be sealed after the cables have been installed. 4 Grounding Protection and Lightning Protection 4.1 Grounding Protection 4.1.1 When a transformer with a low-voltage side of 380/220V and directly grounded neutral is installed at the construction site for construction purposes, the low-voltage side shall adopt a system in which the protective conductor and the neutral conductor are grounded separately (TN-S system) (Figure 4.1.1-1), or a system in which the power supply is grounded while the protective conductor is grounded locally (TT system) (4.1.1-2). However, low-voltage systems powered by the same power source should not use both of the above systems simultaneously. Figure 4.1.1-1 TN-S system; Figure 4.1.1-2 TT system. 4.1.2 The metal enclosures of Class I electrical equipment, as well as the metal frameworks connected to such equipment, must be provided with reliable grounding protection. Note: The classification of Class I electrical equipment shall comply with the provisions of the current ** standards. 4.1.3 The neutral grounding protection shall comply with the following provisions: 4.1.3.1 When the distance between the end of an overhead line, the main distribution panel, and the local distribution box and the power transformer is more than 50 m, their protective neutral wires (PE wires) shall be grounded repeatedly, with the grounding resistance value not exceeding 10 Ω. 4.1.3.2 The working neutral wire and the protective neutral wire connected to electrical equipment must be separated. Switches or fuses must not be installed on the protective neutral wire. 4.1.3.3 The material of the protective neutral wire and the phase wires shall be the same, and the minimum cross-sectional area of the protective neutral wire shall comply with the requirements in Table 4.1.3. Minimum cross-sectional area of the protective neutral wire: Table 4.1.3. 4.1.3.4 The protective neutral wire connected to mobile electric tools or hand-held electric tools must be a copper-core flexible wire; its cross-sectional area should not be less than 1/3 of that of the phase wire, and it must be at least 1.5 mm2. 4.1.4 The protective ground wire or protective neutral wire of electrical equipment shall be connected to ground in parallel; series connection to ground or to the neutral wire is strictly prohibited. 4.1.5 When the construction site does not have a separate transformer with a low-voltage side of 380/220V and a directly grounded neutral point, but instead makes use of the existing power supply system, electrical equipment shall be protected by bonding to the neutral or grounding in accordance with the requirements of the original system. 4.1.6 The protective ground wire or protective neutral wire shall be connected by welding, crimping, bolt connection, or other reliable methods. Wrapping or hooking is strictly prohibited. 4.1.7 The protective ground wire for low-voltage electrical equipment may use natural grounding elements such as metal components or the rebar in reinforced concrete members; however, it is strictly prohibited to use metal pipes used for transporting flammable liquids, flammable gases, or explosive gases as protective ground wires. 4.1.8 When using a natural grounding electrode as a protective ground wire, the following requirements shall be met: 4.1.8.1 Ensure that its entire length forms a complete electrical path. 4.1.8.2 When using series-connected metal components as protective ground wires, metal connection wires shall be welded at the points where the components are connected in series, and their cross-sectional area shall not be less than 100 mm2. 4.2 Lightning Protection 4.2.1 Substations and distribution stations located in mountainous areas or regions with frequent lightning strikes should be equipped with separate lightning rods ； Lightning arresters or discharge gaps should be installed on high-voltage overhead lines and the high-voltage sides of transformers. 4.2.2 For hoist frames, scaffolding, buildings under construction, as well as facilities such as tower cranes, machinery, chimneys, and water towers at construction sites and temporary living areas that are 20 meters or taller, lightning protection systems must be installed. 4.2.3 For large steel formwork with a height of over 20m, it should be connected to the building’s grounding wire promptly after being in place. 5 Common Electrical Equipment 5.1 General Provisions 5.1.1 The electrical equipment used shall comply with the requirements of current **standards, and must be accompanied by appropriate certification documents; the equipment shall also have nameplates. 5.1.2 Electrical equipment in use should be kept in good working condition; operation with faults is strictly prohibited. 5.1.3 Electrical equipment must not be operated beyond the specifications indicated on its nameplate. 5.1.4 Fixed electrical equipment shall be fully labeled. 5.2 Distribution Boxes and Switch Boxes 5.2.1 Distribution boxes and switch boxes should be installed firmly to facilitate operation and maintenance. 5.2.2 For distribution boxes and switch boxes installed on the ground, the installation location should be flat and above the ground level, with no miscellaneous items piled up in the vicinity. 5.2.3 The inlet and outlet ports of distribution boxes and switch boxes should be located at the bottom or sides of the box; the power leads should be enclosed in pipes equipped with waterproof elbows. 5.2.4 The wires in the distribution boxes and switch boxes shall have good insulation, be arranged neatly, and fixed firmly; the wire ends shall be connected by bolts or crimping. 5.2.5 Distribution boxes with 3 or more circuits shall be equipped with a main disconnect switch and branch disconnect switches. Each branch circuit disconnect switch shall not be connected to 2 or more electrical devices, nor shall it be used by 2 or more work teams. 5.2.6 Distribution boxes that combine lighting and power supply should be equipped with disconnect switches or circuit breakers separately. 5.2.7 Electrical equipment such as contactors, disconnect switches, and switches installed in distribution boxes and switch boxes shall operate smoothly, provide reliable contact, and show no signs of severe arcing or wear on their contacts. 5.3 Fuses and sockets 5.3.1 The specifications of fuses shall meet the requirements of the circuits and equipment being protected ； The melt shall not be thinned or used in multiple strands; it is strictly prohibited to use metal wires as substitutes for fuses. 5.3.2 The melt shall have a protective cover. Tube fuses must not be used without their tubes ； Fuses with filler materials must not be modified for use. 5.3.3 After the melt fuse blows, the cause must be identified and the fault resolved before replacement is possible ； Power can be supplied only after the protective cover is installed. 5.3.4 It is strictly prohibited to use substandard melt in place of the original melt when replacing it. 5.3.5 Pins and sockets must be used together. Class I electrical equipment should use three-hole sockets that can be connected to a protective wire, with its protective terminal connected to the protective earth wire or protective neutral wire. 5.4 Mobile Power Tools and Handheld Power Tools 5.4.1 The management, use, inspection, and maintenance of handheld power tools shall comply with the provisions of the current **standard \"Safety Technical Regulations for the Management, Use, Inspection, and Maintenance of Handheld Power Tools\". 5.4.2 Mobile electric tools and hand-held electric tools that have been out of use for an extended period or have been newly acquired should be inspected and have their insulation tested before use. 5.4.3 Mobile power tools and hand-held power tools shall be provided with protective grounding or protective neutral connection before being powered on. 5.4.4 Mobile power tools and hand-held power tools shall be equipped with separate power switches and protections; it is strictly prohibited to connect two or more power tools to a single switch. 5.4.5 The power switch for portable power tools shall be controlled by a double-pole switch, which shall be installed in a location that is easy to operate. 5.4.6 When portable power tools and hand-held power tools are connected via sockets, their plugs and sockets must be free from damage or cracks, and must have good insulation. 5.4.7 When leaving the work site temporarily due to certain reasons while using a portable power tool, or in case of a sudden power outage, the power switch should be turned off. 5.4.8 Mobile power tools and hand-held power tools shall be equipped with high-sensitivity leakage protectors. 5.4.9 The power cords for mobile power tools and hand-held power tools must be multi-strand rubber-sheathed flexible cables with copper cores, or flexible cables with polyvinyl chloride insulation and polyvinyl chloride sheathing. Cables should be kept away from heat sources and must not be dragged on the ground. When the above requirements cannot be met, measures such as preventing heavy objects from crushing the cables should be taken. 5.4.10 When moving portable power tools and hand-held power tools, the power cord or rotating parts must not be held by hand. 5.4.11 After using portable power tools and hand-held power tools, the power supply must be disconnected at the power source side. 5.4.12 When using hand-held power tools, insulating gloves should be worn or one should stand on an insulating platform. 5.5 Welding Machines 5.5.1 Depending on the construction requirements, welding machines should be installed in groups by area or floor level, and numbered. 5.5.2 Welding machines installed outdoors should be placed in a dry area and covered with a shelter. 5.5.3 The enclosure of the welding machine shall be reliably grounded; multiple units shall not be grounded in series. 5.5.4 The hot insulation resistance value of each coil of the welding machine to its casing shall not be less than 0.4 MΩ. 5.5.5 The exposed conductive parts and rotating parts of the welding machine shall be equipped with safety guards. After the regulator of the DC welding machine is removed, protective covers should be installed over the holes that appear on the casing. 5.5.6 The power cable on the primary side of the welding machine must be properly insulated; it should not be dragged around, and its length should not exceed 5 meters. 5.5.7 The power switch for the welding machine should be provided separately. The power supply of a DC welding machine should be controlled by a starter. 5.5.8 The insulation of the welding torch must be in good condition. 5.5.9 The secondary lead of the welding machine should be a flexible copper cable with rubber insulation, and its length should not exceed 30 m. 5.6 Cranes 5.6.1 The installation of electrical equipment in cranes shall comply with the provisions of the current **standard, namely the ‘Code for Construction and Acceptance of Electrical Equipment in Cranes for Electrical Installation Works’. 5.6.2 The electrical equipment on tower cranes shall meet the requirements specified in the current **standard, ‘Safety Regulations for Tower Cranes’. 5.6.3 The length of the crane’s power cable shall meet the product’s technical requirements. 5.6.4 The area around the power cable retraction path of the track crane should be kept clean; no other equipment, materials, or debris should be stored there. 5.6.5 The automatic wire-winding device of the track crane must operate in a flexible and reliable manner ； Cables must not be dragged on the ground. 5.6.6 Switches that can cut off the power supply shall be provided on or near medium and small cranes. 5.6.7 The power cables of lifting machinery should be inspected regularly, and dedicated personnel should be assigned for maintenance when necessary. 5.6.8 The electrical equipment and wiring on the crane must not be altered without the approval of the relevant personnel. 5.6.9 The electrical equipment on the crane should be inspected regularly, and any defects found should be addressed promptly. No electrical maintenance work shall be carried out during the lifting process. 5.6.10 The maintenance and trial operation of the crane’s electrical equipment require the cooperation of personnel from other specialties. 5.6.11 The lightning protection and grounding of tower cranes shall comply with the provisions of the current **standard \"Safety Regulations for Tower Cranes\" as well as the product’s technical requirements, and their grounding must be reliable. When using a natural grounding electrode, a good electrical path must be ensured. 5.6.12 A set of grounding devices shall be installed at each end of the tracks of a track-mounted crane; when the tracks are long, an additional set of grounding devices shall be installed every 20 meters. 6 Special Environments 6.1 Flammable and Explosive Environments 6.1.1 The selection and installation of electrical equipment and power lines for power supply and use at construction sites shall comply with the provisions of the current ** standards, namely the “Code for Design of Electrical Installations in Explosive and Fire-Hazardous Environments” and the “Code for Construction and Acceptance of Electrical Installations in Explosive and Fire-Hazardous Environments”. 6.1.2 Sparks are strictly prohibited in flammable and explosive environments. When the requirements cannot be met, safety measures should be taken. 6.1.3 Explosion-proof lighting fixtures should be used, and the wiring shall be made of explosion-proof rubber-insulated wires. 6.1.4 Explosion-proof measures shall be taken when using handheld or mobile power tools. 6.1.5 Working on live circuits is strictly prohibited. The power supply must be turned off when replacing the bulb. 6.1.6 The exposed conductive parts of electrical equipment that are not under voltage under normal conditions must be grounded or connected to the neutral. The protective neutral wire must not be disconnected arbitrarily ； When disconnection is necessary, safety measures should be taken, and it should be restored immediately after the work is completed. 6.2 Corrosive Environments 6.2.1 Substations and distribution stations should be located downwind of the wind direction with the lowest frequency throughout the year; they should not be situated downwind of areas where corrosive substances are present. 6.2.2 The minimum distance between substations, distribution stations, and severely corrosive areas shall comply with the provisions in Table 6.2.2. Minimum distance (m) between substations, distribution stations, and highly corrosive areas Table 6.2.2 Note: The determination of Class I and Class II corrosion environments shall comply with the provisions of **current standard specifications. 6.2.3 When 6–10 kV distribution installations are installed outdoors, outdoor corrosion-resistant electrical equipment should be selected. 6.2.4 When 6–10 kV distribution installations are installed indoors, indoor corrosion-resistant electrical equipment should be selected. For the outdoor part of indoor power distribution installations, electrical equipment with one or two higher voltage levels can be used. 6.2.5 When overhead lines are used for 10 kV and lower voltage lines in corrosive environments, concrete poles, angle steel crossarms, and pollution-resistant insulators shall be employed. The rated voltage of insulators and wall bushings should be increased by one or two grades. For overhead lines of 1 kV and below, plastic-insulated wires or anti-corrosion aluminum stranded wires are recommended. For overhead lines of 1 kV and above, aluminum conductor with steel core resistant to corrosion is recommended. 6.2.6 Distribution lines should preferably use fully plastic cables laid exposed. In Class I and Class II corrosive environments, it is not advisable to use the method of installing insulated wires in conduits or laying cables in cable trenches. 6.2.7 There should be no joints in the cable conductors in corrosive environments. The ends of the cable conductors should be connected to the equipment using lugs. 6.2.8 Sealing and anti-corrosion measures shall be taken at the cable inlet and outlet of equipment such as sealed distribution boxes and control boxes. 6.2.9 Copper conductors shall be used for overhead lines in severely corrosive environments. 6.2.10 In heavily corrosive environments, corrosion-resistant, sealed lighting fixtures should be used. 6.3 Particularly Humid Environments 6.3.1 In particularly humid environments, electrical equipment, cables, wires, etc., should be of enclosed or moisture-resistant types. 6.3.2 The metal enclosures, metal frames, and pipelines of electrical equipment shall be properly grounded. 6.3.3 Mobile power tools and hand-held power tools shall be equipped with leakage protectors or use double-insulated equipment. Electric tools that have not been in use for a long time should have their insulation checked before use. 6.3.4 The voltage of the working light should not exceed 12V. 6.3.5 Live work should not be carried out in humid environments; for regular work, insulating boots should be worn or one should stand on an insulating platform. 7 Lighting 7.0.1 Lighting fixtures and equipment must be properly insulated and must comply with the provisions of the current **relevant standards. 7.0.2 The lighting wiring should be neatly arranged and relatively fixed. The hanging height of fixed lighting fixtures installed indoors shall not be less than 2.5 m, while that of lighting fixtures installed outdoors shall not be less than 3 m. Lighting fixtures installed in outdoor work areas should use waterproof lamp bases. 7.0.3 In field offices, dormitories, and work sheds, lighting cables, except for rubber-sheathed flexible cables and plastic-sheathed cables, shall be fixed to insulators and laid separately ； Insulated tubing should be used when passing through walls. 7.0.4 The lighting power supply cables must not come into contact with wet surfaces, must not be placed near heat sources, and must not be directly attached to metal frameworks. When installing temporary lighting on scaffolds, insulators should be added to bamboo and wooden scaffolds, while wooden crossbeams and insulators should be used on metal scaffolds. 7.0.5 The lighting switch shall control the phase wire. When using a screw-base lamp holder, the phase wire should be connected to the center contact. 7.0.6 The use of row lights shall meet the following requirements: 7.0.6.1 The voltage shall not exceed 36V. 7.0.6.2 The voltage of portable lights used in metal containers and metal pipes shall not exceed 12V. 7.0.6.3 The walking light shall be equipped with a protective cover. 7.0.6.4 The handle of the walking light shall be well insulated and heat-resistant as well as moisture-resistant. 7.0.6.5 The power cable for the working light shall be a rubber-sheathed flexible cable. 7.0.6.6 The headlamp transformer must be of the double-winding type. Fuses should be installed on both the primary and secondary sides of the street light transformer ； The metal enclosure should be properly protected with grounding or neutral connection. 7.0.7 It is strictly prohibited to use row light transformers inside metal containers or metal pipes. 7.0.8 Lighting fixtures shall not be installed directly above the distribution panels, distribution cabinets, and busbars in substations and distribution stations (except for enclosed busbars and enclosed distribution panels and cabinets). 7.0.9 A certain safety distance should be maintained between lighting fixtures and flammable materials; for ordinary fixtures, this distance should not be less than 300 mm ； High-heat lighting fixtures such as spotlights and iodine-tungsten lamps should have a distance of no less than 500 mm, and must not shine directly on flammable materials. When the spacing is insufficient, insulation measures should be taken. 8 Safety Technology Management 8.0.1 Before power supply and consumption facilities come online, the entity using electricity should establish and improve a management structure for electricity use, organize specialized teams for operation and maintenance, and clarify the responsibilities of these management structures and teams. 8.0.2 Electricity-consuming units shall establish and improve regulations for the operation and maintenance of power supply and consumption facilities ； Operators and maintenance personnel must learn these operating procedures and become familiar with their organization’s power supply and consumption system. 8.0.3 Electrical users must establish a post responsibility system for electrical safety, clearly defining the persons in charge of electrical safety at each level. 8.0.4 Personnel responsible for the operation and maintenance of electrical facilities must meet the following requirements: 8.0.4.1 They must be free from any health conditions that, as determined by a doctor, would prevent them from performing electrical work. 8.0.4.2 Master the necessary electrical knowledge, pass the examination, and obtain a certificate of completion. 8.0.4.3 Master touch electrical rescue methods and artificial respiration techniques. 8.0.5 The operating and maintenance personnel of electrical users must study and be familiar with the relevant provisions of these specifications, and shall take an exam once a year. Those who have interrupted their work for more than 3 consecutive months due to certain reasons must relearn these regulations and pass an examination before they can resume electrical work. 8.0.6 New maintenance electricians, temporary workers, and interns must receive safety training before starting work; only after passing the relevant tests and under the supervision of qualified electricians can they undertake the assigned tasks. 8.0.7 Requirements for the personnel on duty at the substation (power distribution station): 8.0.7.1 Familiarity with the system, operation mode, and performance of electrical equipment in this substation (power distribution station). 8.0.7.2 Work with a valid certificate and master operational techniques. 8.0.7.3 Be able to conscientiously implement various rules and regulations established by the unit. 8.0.8 The person in charge of duty or the individual on duty at the substation (power distribution station) should be a person with practical experience. 8.0.9 When the duty personnel at the substation (power distribution station) are on duty alone, they shall not carry out maintenance work. 8.0.10 Substations (distribution stations) must be equipped with sufficient safety tools and protective devices such as insulating gloves, insulating rods, insulating mats, and insulating platforms. 8.0.11 For the operation and maintenance of power supply and consumption facilities, sufficient electrical insulation tools must be available, and electrical performance tests must be carried out regularly in accordance with relevant regulations. Electrical insulation tools must never be used for other purposes. 8.0.12 All electrical installations should be inspected regularly, and the details of each inspection as well as any problems identified should be recorded in the operation log. 8.0.12.1 For low-voltage distribution installations, low-voltage electrical apparatus, and transformers, inspections shall be carried out once per shift when there is a person on duty. When unattended, it should be inspected at least once a week. 8.0.12.2 The distribution panel should be inspected once per shift. 8.0.12.3 The inspection of overhead lines shall be carried out at least once per quarter. 8.0.12.4 Distribution panels and distribution boxes with a voltage of 1 kV or less installed in workshops or construction sites should be inspected and cleaned during a power outage once per quarter. 8.0.12.5 Iron-clad switches with a voltage of 500V or less, as well as other switches whose cutters cannot be seen directly, should be inspected once a month. 8.0.13 In addition to regular maintenance, electrical facilities at outdoor construction sites should be subject to increased inspection and monitoring during severe weather conditions such as strong winds, heavy rain, hail, snow, frost, and fog ； During inspections and checks, insulated boots must be worn, and one must not approach lightning arresters and lightning rods. 8.0.14 For electrical equipment that has just been put into operation or put into operation after major maintenance, inspections should be intensified within 72 hours; only after no abnormalities are detected can inspections be carried out at the regular interval. 8.0.15 The cleaning and maintenance of power supply and consumption facilities should be carried out at least twice a year, and these tasks should be scheduled before the rainy season and winter arrive. 8.0.16 When performing maintenance on electrical equipment or circuits with power outage, the following regulations shall be followed: 8.0.16.1 The primary equipment must be completely de-energized, and the switches or fuses on the secondary sides of transformers and voltage transformers must also be turned off. 8.0.16.2 The grounding wire may be installed and work may proceed only after the power supply to the equipment or circuit has been cut off and it has been confirmed that there is no voltage present. 8.0.16.3 Appropriate signs should be hung at all work locations. 8.0.17 A supervisor shall be assigned when working near live parts. The normal operating range of personnel at work and the minimum safe distance from live equipment shall comply with the provisions of Table 8.0.17. Table 8.0.17: Normal activity range of staff and minimum safe distance from live equipment; Table 8.0.18: The management of electricity use shall comply with the following requirements: 8.0.18.1 When electricity is needed on-site, an application must be submitted in advance; upon approval by the electricity management department, the maintenance team will be notified to make the connections. 8.0.18.2 The operation of the starting power supply must be carried out by a maintenance electrician, and a dedicated person should be assigned to supervise it. 8.0.18.3 After the construction electricity has been used, the person in charge of electricity use at the construction site shall notify the maintenance team to remove it. 8.0.18.4 It is strictly prohibited for persons who are not electricians to disassemble or assemble electrical equipment, and it is also strictly prohibited to connect power sources in a haphazard manner. 8.0.18.5 The switch boxes and switch cabinets in the distribution room and at the site shall be locked. 8.0.18.6 Signages stating “Do not approach to avoid electric shock” should be installed in areas where electrical equipment is located. 8.0.18..7 The grounding device should be inspected regularly. 8.0.18.8 Large electrical equipment and heavy machinery at the construction site should be maintained and managed by dedicated personnel. Appendix A Explanation of Terms Used in This Specification A.0.1 To facilitate differentiated treatment when implementing the provisions of this specification, the terms with varying levels of strictness are explained as follows: 1. Terms indicating a very high level of strictness, where action is mandatory: The positive term used is “must”” ； The opposite term is “strictly prohibited”. 2. Indicates strictness; it should be done under normal circumstances: the positive term uses “should”” ； The negative form uses “should not” or “must not”. 3. It indicates that some flexibility is allowed; when conditions permit, this should be done first: positive terms use “should” or “can”” ； The antonym is “not suitable”. A.0.2 Where the provisions state that compliance with other relevant standards and specifications is required, it shall be expressed as “shall meet the requirements of …” or “shall be carried out in accordance with …”. Additional Notes: Lead organization, participating organizations, and main drafters of this standard
Lead organization: Electric Power Construction Research Institute of the Ministry of Electric Power
Participating organizations: Construction Coordination Department of the Ministry of Electric Power, Beijing Electric Power Construction Company, Automation Research Institute of the Ministry of Metallurgy, Professional Design Institute of the Ministry of Railways, Beijing Construction Engineering Group Corporation
Main drafters: Li Gang, Yi Kaisen, Li Zhigeng, Liu Jiping, Zhou Minfeng, Ma Changying, Zhang Chunsheng
Explanations regarding the provisions of the Code for Safety in Power Supply and Use at Construction Sites GB50194-93
Rationale for formulation
In accordance with the requirements set out in Document No. 2630 (1986) issued by the Planning Commission and Document No. 5 (90) issued by the Standards and Quotas Department of the Ministry of Construction, the Ministry of Electric Power was responsible for leading the development of this standard. Specifically, the Electric Power Construction Research Institute of the Ministry of Electric Power took charge of the task, working together with the Professional Design Institute of the Ministry of Railways, the Automation Research Institute of the Ministry of Metallurgy, Beijing Electric Power Construction Company, Beijing Construction Engineering Group Corporation, and the Construction Coordination Department of the Ministry of Electric Power. The standard titled “Code for Safety in Power Supply and Use at Construction Sites” has now been completed. Approved by the Ministry of Construction in its document Jianbiao (1993) No. 22 on December 30, 1993, and issued jointly with the **Technical Supervision Bureau. During the development of this standard, the drafting team collected American standards, former Soviet Union standards, and IEC international standards, as well as relevant domestic local and industry standards and materials. The compilation team focused on investigating the electricity usage and requirements for construction projects in industries such as metallurgy, civil construction, petroleum, coal, and power generation. It sought opinions from relevant organizations across the country, and finally the draft was reviewed and finalized by the Ministry of Electric Power in conjunction with other relevant departments. Given that these specifications are being developed for the first time, it is hoped that during their implementation, various organizations will combine engineering practice with scientific research, carefully summarize experience, and pay attention to accumulating relevant data. If any modifications or additions are necessary, please send your comments and relevant materials to the Electric Power Construction Research Institute (address: Liangxiang, Beijing ； Postal code: 102401) for reference in future revisions. 1 General Provisions 1.0.1 The power supply and electrical facilities at construction sites are generally quite basic, have a short service life, and as the construction progresses, these facilities as well as the electrical load keep changing. Therefore, in order to ensure the safety of personnel and equipment during construction by means of the power supply and distribution systems used in construction, these specifications have been formulated in accordance with **relevant regulations, taking into account the actual conditions and characteristics of various construction sites. 1.0.2 Specifies the scope of application of this standard: construction electrical facilities with a voltage of 10 kV or less. Since further research and experience accumulation are needed regarding electrical power usage in underwater, underground, and tunnel construction, this standard is not applicable to such constructions for the time being. 1.0.3 As construction progresses, the electrical and power supply facilities used in construction need to be frequently disassembled, reassembled, and moved. Therefore, the electricity used for design and construction must be safe and reliable, ensure quality, and be economically reasonable, all within the framework permitted by economic policies. 2 Power generation facilities, substation facilities, distribution facilities 2.1 Power generation facilities 2.1.1 Using diesel generators or other power generation facilities for power supply is uneconomical and unstable. Therefore, it should only be used at construction sites that are far from the power source or where the power source cannot meet the requirements. 2.1.2 The site selection for power generation stations shall meet the following requirements: 2.1.2.1 Be located near load centers in order to reduce investment in distribution facilities and power losses, as well as to minimize power supply failures. 2.1.2.3, 2.1.2.4 Improve the reliability of power supply and consumption. 2.1.3 The layout within the station area shall meet the following requirements: 2.1.3.1 The arrangement of the machine rooms should first satisfy the needs of the production process and operating procedures; the layout of various buildings should be rational and compact, in order to save land use, reduce construction and operating costs, and facilitate maintenance and management. 2.1.3.2 The main consideration is that the noise generated during the operation of the unit and the exhaust fumes it emits cause significant pollution in the downwind direction, while causing less pollution in the upwind direction, in order to reduce the impact of pollution. 2.1.3.3 The water vapor emitted from the water tanks can cause freezing of the outdoor distribution equipment and wires during winter in cold regions, affecting safe operation. Water vapor falling on the walls of the machine room affects the durability of those walls; therefore, the cooling ponds and spray tanks should be located upwind of the machine room and the outdoor power distribution equipment, in the direction of the wind with the lowest frequency during winter. This helps to reduce the amount of water vapor that falls on the power distribution equipment and the walls of the machine room. 2.1.3.4 To prevent water accumulation within the station area and rainwater from entering the station building, thereby affecting the proper operation of the equipment, extensive research has led to the conclusion that a drainage slope of 0.5% within the station area is appropriate. 2.1.4 Diesel power stations primarily use light diesel, which must be filtered before use to prevent debris from clogging the fuel nozzles, fuel injectors, etc.; therefore, two fuel tanks should be installed to allow for alternating use. One is in operation, while the other is used for precipitation treatment. 2.1.5 In accordance with environmental protection requirements, the waste oil, residual oil, and oil discharged as a result of accidents from the power plant must not be poured into ditches or seep into the ground; therefore, oil tanks must be installed for collection, and their capacity is determined based on the aforementioned requirements. The installation of oil tanks must meet fire safety requirements. 2.1.6 Using a single smoke exhaust duct for multiple units increases the smoke exhaust resistance, reduces the output of those units, and makes maintenance difficult; therefore, separate ducts are provided for each unit. The exhaust temperature of diesel engines can reach 400–500°C; therefore, the surfaces of the exhaust pipes installed overhead in the machine room should be equipped with insulation layers. In some power plants, accidents have occurred where oil pipes passing overhead the smoke exhaust pipes laid in the machine room trenches caused oil to drip onto the uninsulated smoke exhaust pipes, leading to fires; therefore, it is required that a fire-resistant insulation layer such as asbestos cement be applied to the surface of the smoke exhaust pipes that pass through these oil pipes. In the sections of the smoke exhaust ducts that run vertically outside the machine room, when they are less than 1 meter away from the walls of the machine room or when they are below the eaves of the machine room by less than 1 meter, hot smoke can easily enter the machine room, mix with oil vapors to form flammable gases, or contaminate the air inside the machine room. 2.1.8 To prevent electric shock to workers caused by damage to the generator’s insulation, trailer grounding measures are adopted. For grounding, a temporary grounding electrode can be used separately, or it can be connected to metal pipes buried underground that do not contain flammable gases or corrosive substances, as well as to the metal framework of buildings that are in reliable contact with the ground. 2.1.11 The prerequisite for determining the total capacity of the unit is to ensure an adequate supply of load; in addition, it is necessary to verify the starting capacity of the largest asynchronous motor. The latter shall start large-capacity squirrel-cage motors at full voltage in accordance with the provisions of the **Standard ‘Basic Technical Requirements for 250 to 300 kW Diesel Generators’, and the maximum instantaneous voltage drop on the generator busbar shall not exceed 20% of the rated value. 2.1.12 Necessary measures to ensure the safe operation of the generator and the stable operation of the unit. 2.1.13 The automatic air switch in the main circuit of the generator is equipped with short-circuit and overload protection devices; the loss-of-voltage trip device of the automatic air switch provides low-voltage protection. 2.2 Substation and distribution facilities 2.2.1 The location selection for substations and distribution stations shall meet the following requirements: 2.2.1.1, 2.2.1.2 Being located near power sources and load centers in order to reduce investment and energy losses and improve the quality of power supply. 2.2.1.3 Substations and distribution stations must not be flooded to ensure normal operation. There should be no water accumulation within the area, so a certain slope for drainage should be considered for the ground. 2.2.1.4 Contamination of the equipment reduces its insulation, posing a threat to safe operation. According to investigations, flashover incidents have occurred in outdoor substations in some heavily polluted areas. 2.2.2.1 Considering the temporary nature of construction electricity use and investment constraints, and in accordance with the relevant provisions of the **Standard ‘Design Code for Industrial and Civil 10kV and Lower Voltage Substations’, the fire resistance ratings of the control room, distribution room, and transformer room were determined while ensuring safety. 2.2.3 The transformer platform has a simple structure, is easy to construct, saves materials, and ensures safe operation; therefore, it is suitable for the installation of small-capacity transformers. 2.5m is above the height that an average person can reach with outstretched arms, ensuring the safety of pedestrians and equipment. 2.2.4 The strength and stability of the transformer station, as well as the selection of secondary-side electrical equipment: Transformers with a capacity of over 400 kVA should not be installed on poles; instead, they should be installed on the ground. In accordance with the relevant provisions of the **Standard ‘Design Code for Industrial and Civil 10kV and Lower Voltage Substations’, necessary installation conditions are specified to ensure the safe operation of transformers and prevent electric shock accidents. 2.2.5 Fuses are used on the high-voltage and low-voltage sides; on the high-voltage side, they serve as protection against internal faults in the transformer ； For the low-voltage side, it serves as overload protection. 2.2.6 In accordance with the relevant provisions of the technical regulations for the design of overhead distribution lines issued by the former Ministry of Water Resources and Electric Power. 2.2.7 It is mainly to prevent the safe operation of the transformer from being affected in case the cable terminal explodes, and to prevent capacitive current from arising between the cable and the transformer. 2.2.8 and 2.2.9 Box-type substations are easy to install and maintain, and their use at construction sites has been increasing in recent years. To ensure safety, during installation and use, in addition to inspecting and testing electrical equipment in accordance with the product’s technical specifications and relevant regulations, it is also necessary to properly ground the enclosure. 3 Imaginary power distribution lines and cable lines 3.1 Selection and installation of utility poles 3.1.1 To save wood, **the use of wooden poles and wooden crossarms is not recommended. However, at construction sites in mountainous areas, it is difficult to transport concrete poles from other places; to facilitate construction, local materials such as wooden poles and wooden crossbeams can be used. 3.1.2.2 This requirement is in place to ensure the quality of pole foundations; in some areas, accidents such as bent poles or even fallen poles have occurred due to poor compaction of the backfill soil. Based on the experience in some areas, compacting once for every 500 mm of fill is sufficient and meets the quality requirements. The anti-settlement foundation refers to the soil accumulation around the pit base after the utility poles are erected. The purpose of adding soil is to prevent the backfilled soil from sinking, which could cause the soil around the utility pole to collapse and affect the stability of its foundation. Based on experience in some areas, it is necessary to install soil retention platforms. 3.1.2.3 The burial depth of utility poles is generally based on 1/6 of the pole’s height. This clause sets out different requirements based on the length of the utility poles; when the design does not specify otherwise, the data provided in this clause may be used. 3.1.2.5 For poles equipped with transformer platforms, an embedding depth of 2m is considered sufficient to ensure safety based on experience. 3.1.3.2 The contents of this clause represent the general rules for distribution lines, and no issues have been encountered as all areas have followed these provisions. 3.1.3.3 This clause is formulated on the basis of summarizing construction experiences from various locations, with the aim of ensuring that the tension rods are subjected to proper stress and thus fulfill their intended function. 3.1.3.4 When the strain conductor passes through between the conductors, it is possible that the shaking strain conductor may come into contact with the conductors, leading to accidents; therefore, it is specified that insulators should be installed when the strain conductor passes through the conductors. The height should exceed what a human hand can reach, hence it is specified at 2.5m. 3.2 Line Installation 3.2.1 The selection of the route and pole locations is a fundamental aspect of line construction; improper selection can threaten the safe operation of the lines and hinder the proper progress of construction. Therefore, based on past experience, several basic requirements are outlined in this section. 3.2.2 At the construction site, there is frequent human activity and a concentration of large machinery, which increases the risk of electric shock accidents. To ensure the safety of personnel and equipment, insulated wires should be used when working in this area. 3.2.3 The construction site is crowded with people and sees frequent traffic of vehicles; therefore, this section adopts the provisions in the **standards regarding the cross-sectional area of overhead line conductors in densely populated areas. Sections 3.2.4–3.2.7 and 3.2.9, 3.2.10 all refer to the relevant provisions of the **standard \"Code for Construction and Acceptance of Electrical Installation Projects – Overhead Distribution Lines of 10 kV and Below\". 3.2.8 The installation curve tables are prepared based on different regions and climate conditions in our country, by using various types of conductors and different cross-sectional areas for them. 3.3 Cable Laying 3.3.1 The construction site is frequently excavated and backfilled; to prevent the cables from being damaged or broken, they should be laid along roadsides or the edges of buildings. To facilitate their identification, maintenance, and protection, markers indicating the path of the cables should be installed along their route. 3.3.2 High-voltage cables, as well as low-voltage cables in areas subject to mechanical damage and frequent traffic from vehicles and people, should be buried at a depth of 0.7 m or more; under normal circumstances, a depth of 0.2 m is sufficient. Sections 3.3.3 and 3.3.5 shall refer to the relevant provisions of the **Standard: Code for Construction and Acceptance of Electrical Installation Projects – Cable Lines Section**. 3.3.4 The installation height of cables is specified to avoid interfering with the normal progress of construction work and the movement of personnel. The construction quality of low-voltage cable terminations is generally poor, and they are prone to water ingress and arcing; therefore, higher standards are required. 4 Grounding Protection and Lightning Protection 4.1 Grounding Protection 4.1.1 In a TN-S grounding system, the PE wire does not carry load current under normal conditions; therefore, the PE wire and the equipment’s casing are not electrified under normal circumstances. They only acquire a potential when a grounding fault occurs. Hence, this system is relatively safe to use at construction sites. However, in some construction sites, the power supply area is large and dispersed; it is somewhat difficult to run 5 wires from the power source, and the long distances and high impedance pose problems when using the TN-S system. Therefore, the TT system should be adopted, with the enclosures of electrical equipment connected directly to the grounding electrode. 4.1.2 In accordance with the relevant provisions of the **Standard ‘Code for Design of Grounding in Industrial and Civil Electrical Installations’, it is determined based on the level of electricity usage at construction sites in China. The metal casing of electrical equipment, as well as the metal frames connected to such equipment, must be reliably connected to the PE protection wire. This is done to prevent the casing from becoming charged in the event of insulation failure of the electrical equipment, thereby avoiding threats to human safety; hence, grounding measures are employed. 4.1.3.1 The purpose of repeated grounding is to reduce the voltage to ground when the equipment enclosure is charged. 4.1.3.2 Provisions made, in light of the characteristics of the construction site, to improve the reliability of the protective neutral wire and prevent errors in its connection or breaks. 4.1.3.3 PE conductor cross-section determined based on thermal stability requirements. 4.1.3.4 The minimum cross-sectional area of the protective neutral wire for mobile or hand-held electric tools, as determined in accordance with the relevant provisions of the **Standard ‘Safety Technical Regulations for the Management, Use, Inspection, and Maintenance of Handheld Electric Tools’**. 4.1.4 To prevent all the following devices from losing protection due to poor contact or disconnection of the protective ground wire or protective neutral wire of a particular device, it is specified that grounding must be done in parallel only, and not in series. 4.1.8 Using natural grounding electrodes facilitates construction, ensures reliable grounding, and saves materials. Operational experience has shown that in areas with low soil resistivity, it is possible to avoid the need for artificial grounding electrodes when natural ones are utilized. 4.2 Lightning Protection 4.2.2 It is determined in accordance with the requirements of the **Standards for Safety of Tower Cranes and Code for Design of Lightning Protection in Buildings**, taking into account the height of construction machinery and structures at the construction site. 5 Common Electrical Equipment 5.2 Distribution Boxes and Switch Boxes 5.2.1–5.2.3 specify the requirements for the environment surrounding distribution boxes and switch boxes, to facilitate wiring, cable connections, and maintenance, thereby ensuring safe and reliable operation. 5.2.5 Easy to use, maintain, and repair. 5.2.6 Separate switches are provided for lighting and power supply; this is to ensure the safety of lighting circuits and to prevent lighting from being affected by faults in the power supply lines. 5.4 Mobile power tools and hand-held power tools 5.4.3 This requirement shall be met using a three-core rubber-sheathed flexible cable. 5.4.4 To prevent a malfunction in one power tool from affecting the use of other power tools, as well as to facilitate use, inspection, and maintenance. 5.4.7 Prevent sudden rotation of powered tools to avoid accidents. 5.4.8 Complies with the relevant provisions of the **Standard ‘Safety Technical Regulations for the Management, Use, Inspection, and Maintenance of Handheld Electric Tools’. 5.4.12 Prevent accidental electric shock. 5.5 Welding Machines 5.5.1 Centralized power supply is necessary for easier management, to prevent accidents, and to ensure proper construction practices. 5.5.2～5.5.8 The requirements for the location of welding machines, as well as the regulations regarding grounding, are specified in accordance with the needs for moisture protection, fire prevention, and electric shock prevention. 5.5.9 The secondary lead of the welding machine is often dragged along the ground as the construction site changes, and the conditions at the construction site are poor, which can easily damage the welding wire; therefore, it is necessary to use high-quality rubber-sheathed flexible cables. 5.6 Cranes 5.6.4 Equipment and miscellaneous items stored near the tracks can interfere with the retraction and extension of cables, and they may also damage the cables, thereby leading to accidents; hence this requirement is stipulated. 5.6.6 Medium and small cranes are generally operated using button switches on the ground, with a power switch installed on or near the crane to allow for immediate power disconnection in case of an accident. 5.6.8 Making arbitrary changes to electrical equipment and wiring methods can affect the operator’s familiarity with the equipment, increasing the risk of operational errors. 5.6.9 Prevent maintenance and operation of electrical equipment from affecting the operation of other related specialties, as well as personal safety and equipment safety. Inspecting equipment during lifting processes interferes with the lifting operation and can easily lead to lifting accidents. 5.6.11 Improve the reliability of grounding protection and ensure the required grounding resistance. 6 Special Environments 6.1 Flammable and Explosive Environments 6.1.3–6.1.5 The use of explosion-proof equipment and the implementation of explosion-proof measures are aimed at preventing the generation of sparks and reducing the occurrence of fires and explosions. 6.1.6 In accordance with the provisions of the **Standards: Code for Design of Electrical Installations in Explosive and Fire-Hazardous Environments** and **Code for Construction and Acceptance of Electrical Installations in Explosive and Fire-Hazardous Areas for Electrical Installation Projects**. 6.2 Corrosive Environment 6.2.1 The so-called dominant wind direction refers to the single wind direction with the highest frequency of occurrence within a year. Prevent corrosive substances from damaging electrical equipment, thereby avoiding a reduction in insulation or its destruction. 6.2.2 The principles for determining the corrosion protection distance take into account both staying away from sources of corrosive substances and minimizing line losses as well as saving land use. The definitions of Class I corrosion environments and Class II corrosion environments are provided in the \"Technical Regulations for Electrical Design in Corrosive Environments of Chemical Enterprises\". 6.2.5 Due to the poor chemical resistance of wood, cement poles and angle steel crossarms are used. There is years of operational experience in various regions using higher voltage levels to enhance insulation. 6.2.6 All-plastic cables (cables with plastic insulation and plastic sheathing) possess excellent electrical properties and reliable corrosion resistance; Chinese chemical enterprises have many years of experience in using such cables in operational settings. The method of installing insulated wires in conduits is complicated to implement; it leads to easy corrosion and moisture damage, results in poor electrical insulation properties, and incurs high operating costs. With the cable trench installation method, cables are prone to corrosion and water damage within the trenches, as well as mechanical damage, which shortens their service life. Hence, these regulations were established. 6.2.7 Reliable measures for safe power supply and use in corrosive environments. Improve the reliability of joint connections. 6.2.8 Cable entry and exit points for distribution boxes, control boxes, etc., in corrosive environments should be equipped with cable sealing sleeves; manufacturers are able to supply these as part of their products. During construction, attention must be paid to implementing proper sealing and anti-corrosion measures at these cable entry and exit points. 6.2.9 Copper-core wires have good corrosion resistance, but their cost is high; therefore, they are used only in highly corrosive environments. 6.3 Particularly humid environments An environment is considered humid when its relative humidity is consistently above 75%, while it is regarded as particularly humid when the relative humidity is close to 100%. When performing electrical work in particularly humid environments, it is necessary to follow the five most basic principles outlined in this section. Special care must be taken when using mobile or portable power tools; installing leakage protectors, wearing insulating boots, and working on an insulating platform are all effective measures to ensure safety. 7 Lighting 7.0.2 Refer to the relevant provisions in the section on electrical lighting installations of the national standard \"Code for Construction and Acceptance of Electrical Installation Projects\". The hanging height of the lighting fixtures is determined based on the actual conditions at the construction site. 7.0.4 Some requirements established to prevent a decrease in insulation or insulation failure. 7.0.5 General requirements for protection against electric shock. 7.0.6 Refer to the relevant provisions in the Electrical Lighting Devices section of the national standard \"Code for Construction and Acceptance of Electrical Installation Projects\". 7.0.7 Prevent the metal containers or pipes from becoming electrified in the event of insulation failure on the primary side of the track light transformer. 7.0.8 This is specified to ensure that maintenance personnel are not at risk of electric shock when servicing distribution panels, switchgear, and busbars, while also taking into account the need to avoid disruptions to power supply and consumption. 7.0.9 Fire protection requirements derived from operational experience. 8 Safety Technology Management 8.0.1～8.0.3 Strengthening the management of power supply and consumption, as well as the necessary organizational and technical measures to ensure safe power supply and consumption. 8.0.4 Necessary qualifications for operators and maintenance personnel of construction electricity. 8.0.8, 8.0.9 To ensure the personal safety of the personnel on duty as well as the safety of the equipment during operation, maintenance, and other activities, it is necessary to have certain essential safety equipment and measures in place. 8.0.11 Severe weather can lead to accidents such as pole collapse, wire breaks, damage to electrical equipment, and reduced insulation; therefore, inspections and surveillance should be intensified. To ensure the safety of inspectors, proper protection should be in place during inspections. 8.0.12 New equipment and equipment that has been overhauled shall undergo a 72-hour trial run; it can be put into formal operation only after passing this test. 8.0.13 specifies the cleaning and maintenance cycles for power supply and consumption facilities. 8.0.14 and 8.0.15 refer to the provisions of the Ministry of Energy’s \"Safety Regulations for the Electric Power Industry\" (Electrical Part for Power Plants and Substations). 8.0.16.1 To strengthen the management of electrical load. 8.0.16.2 To ensure the safety of maintenance personnel, a supervisor must be assigned. 8.0.16.3 Removing it promptly after use ensures safety and prevents the loss of equipment and supplies. 8.0.16.4 Electrical work is a type of special task that requires training; one must pass relevant examinations before being allowed to carry out electrical work properly, as otherwise accidents are likely to occur. Generally, those who have not taken the exam are prohibited from tampering with electrical equipment. 8.0.16.5 is intended to prevent electric shock and misuse of power supply facilities.
Lead organization: Electric Power Construction Research Institute of the Ministry of Electric Power
Participating organizations: Construction Coordination Department of the Ministry of Electric Power, Beijing Electric Power Construction Company, Automation Research Institute of the Ministry of Metallurgy, Professional Design Institute of the Ministry of Railways, Beijing Construction Engineering Group Corporation
Main drafters: Li Gang, Yi Kaisen, Li Zhigeng, Liu Jiping, Zhou Minfeng, Ma Changying, Zhang Chunsheng
Explanations regarding the provisions of the Code for Safety in Power Supply and Use at Construction Sites GB50194-93
Rationale for formulation
In accordance with the requirements set out in Document No. 2630 (1986) issued by the Planning Commission and Document No. 5 (90) issued by the Standards and Quotas Department of the Ministry of Construction, the Ministry of Electric Power was responsible for leading the development of this standard. Specifically, the Electric Power Construction Research Institute of the Ministry of Electric Power took charge of the task, working together with the Professional Design Institute of the Ministry of Railways, the Automation Research Institute of the Ministry of Metallurgy, Beijing Electric Power Construction Company, Beijing Construction Engineering Group Corporation, and the Construction Coordination Department of the Ministry of Electric Power. The standard titled “Code for Safety in Power Supply and Use at Construction Sites” has now been completed. Approved by the Ministry of Construction in its document Jianbiao (1993) No. 22 on December 30, 1993, and issued jointly with the **Technical Supervision Bureau. During the development of this standard, the drafting team collected American standards, former Soviet Union standards, and IEC international standards, as well as relevant domestic local and industry standards and materials. The compilation team focused on investigating the electricity usage and requirements for construction projects in industries such as metallurgy, civil construction, petroleum, coal, and power generation. It sought opinions from relevant organizations across the country, and finally the draft was reviewed and finalized by the Ministry of Electric Power in conjunction with other relevant departments. Given that these specifications are being developed for the first time, it is hoped that during their implementation, various organizations will combine engineering practice with scientific research, carefully summarize experience, and pay attention to accumulating relevant data. If any modifications or additions are necessary, please send your comments and relevant materials to the Electric Power Construction Research Institute (address: Liangxiang, Beijing ； Postal code: 102401) for reference in future revisions. 1 General Provisions 1.0.1 The power supply and electrical facilities at construction sites are generally quite basic, have a short service life, and as the construction progresses, these facilities as well as the electrical load keep changing. Therefore, in order to ensure the safety of personnel and equipment during construction by means of the power supply and distribution systems used in construction, these specifications have been formulated in accordance with **relevant regulations, taking into account the actual conditions and characteristics of various construction sites. 1.0.2 Specifies the scope of application of this standard: construction electrical facilities with a voltage of 10 kV or less. Since further research and experience accumulation are needed regarding electrical power usage in underwater, underground, and tunnel construction, this standard is not applicable to such constructions for the time being. 1.0.3 As construction progresses, the electrical and power supply facilities used in construction need to be frequently disassembled, reassembled, and moved. Therefore, the electricity used for design and construction must be safe and reliable, ensure quality, and be economically reasonable, all within the framework permitted by economic policies. 2 Power generation facilities, substation facilities, distribution facilities 2.1 Power generation facilities 2.1.1 Using diesel generators or other power generation facilities for power supply is uneconomical and unstable. Therefore, it should only be used at construction sites that are far from the power source or where the power source cannot meet the requirements. 2.1.2 The site selection for power generation stations shall meet the following requirements: 2.1.2.1 Be located near load centers in order to reduce investment in distribution facilities and power losses, as well as to minimize power supply failures. 2.1.2.3, 2.1.2.4 Improve the reliability of power supply and consumption. 2.1.3 The layout within the station area shall meet the following requirements: 2.1.3.1 The arrangement of the machine rooms should first satisfy the needs of the production process and operating procedures; the layout of various buildings should be rational and compact, in order to save land use, reduce construction and operating costs, and facilitate maintenance and management. 2.1.3.2 The main consideration is that the noise generated during the operation of the unit and the exhaust fumes it emits cause significant pollution in the downwind direction, while causing less pollution in the upwind direction, in order to reduce the impact of pollution. 2.1.3.3 The water vapor emitted from the water tanks can cause freezing of the outdoor distribution equipment and wires during winter in cold regions, affecting safe operation. Water vapor falling on the walls of the machine room affects the durability of those walls; therefore, the cooling ponds and spray tanks should be located upwind of the machine room and the outdoor power distribution equipment, in the direction of the wind with the lowest frequency during winter. This helps to reduce the amount of water vapor that falls on the power distribution equipment and the walls of the machine room. 2.1.3.4 To prevent water accumulation within the station area and rainwater from entering the station building, thereby affecting the proper operation of the equipment, extensive research has led to the conclusion that a drainage slope of 0.5% within the station area is appropriate. 2.1.4 Diesel power stations primarily use light diesel, which must be filtered before use to prevent debris from clogging the fuel nozzles, fuel injectors, etc.; therefore, two fuel tanks should be installed to allow for alternating use. One is in operation, while the other is used for precipitation treatment. 2.1.5 In accordance with environmental protection requirements, the waste oil, residual oil, and oil discharged as a result of accidents from the power plant must not be poured into ditches or seep into the ground; therefore, oil tanks must be installed for collection, and their capacity is determined based on the aforementioned requirements. The installation of oil tanks must meet fire safety requirements. 2.1.6 Using a single smoke exhaust duct for multiple units increases the smoke exhaust resistance, reduces the output of those units, and makes maintenance difficult; therefore, separate ducts are provided for each unit. The exhaust temperature of diesel engines can reach 400–500°C; therefore, the surfaces of the exhaust pipes installed overhead in the machine room should be equipped with insulation layers. In some power plants, accidents have occurred where oil pipes passing overhead the smoke exhaust pipes laid in the machine room trenches caused oil to drip onto the uninsulated smoke exhaust pipes, leading to fires; therefore, it is required that a fire-resistant insulation layer such as asbestos cement be applied to the surface of the smoke exhaust pipes that pass through these oil pipes. In the sections of the smoke exhaust ducts that run vertically outside the machine room, when they are less than 1 meter away from the walls of the machine room or when they are below the eaves of the machine room by less than 1 meter, hot smoke can easily enter the machine room, mix with oil vapors to form flammable gases, or contaminate the air inside the machine room. 2.1.8 To prevent electric shock to workers caused by damage to the generator’s insulation, trailer grounding measures are adopted. For grounding, a temporary grounding electrode can be used separately, or it can be connected to metal pipes buried underground that do not contain flammable gases or corrosive substances, as well as to the metal framework of buildings that are in reliable contact with the ground. 2.1.11 The prerequisite for determining the total capacity of the unit is to ensure an adequate supply of load; in addition, it is necessary to verify the starting capacity of the largest asynchronous motor. The latter shall start large-capacity squirrel-cage motors at full voltage in accordance with the provisions of the **Standard ‘Basic Technical Requirements for 250 to 300 kW Diesel Generators’, and the maximum instantaneous voltage drop on the generator busbar shall not exceed 20% of the rated value. 2.1.12 Necessary measures to ensure the safe operation of the generator and the stable operation of the unit. 2.1.13 The automatic air switch in the main circuit of the generator is equipped with short-circuit and overload protection devices; the loss-of-voltage trip device of the automatic air switch provides low-voltage protection. 2.2 Substation and distribution facilities 2.2.1 The location selection for substations and distribution stations shall meet the following requirements: 2.2.1.1, 2.2.1.2 Being located near power sources and load centers in order to reduce investment and energy losses and improve the quality of power supply. 2.2.1.3 Substations and distribution stations must not be flooded to ensure normal operation. There should be no water accumulation within the area, so a certain slope for drainage should be considered for the ground. 2.2.1.4 Contamination of the equipment reduces its insulation, posing a threat to safe operation. According to investigations, flashover incidents have occurred in outdoor substations in some heavily polluted areas. 2.2.2.1 Considering the temporary nature of construction electricity use and investment constraints, and in accordance with the relevant provisions of the **Standard ‘Design Code for Industrial and Civil 10kV and Lower Voltage Substations’, the fire resistance ratings of the control room, distribution room, and transformer room were determined while ensuring safety. 2.2.3 The transformer platform has a simple structure, is easy to construct, saves materials, and ensures safe operation; therefore, it is suitable for the installation of small-capacity transformers. 2.5m is above the height that an average person can reach with outstretched arms, ensuring the safety of pedestrians and equipment. 2.2.4 The strength and stability of the transformer station, as well as the selection of secondary-side electrical equipment: Transformers with a capacity of over 400 kVA should not be installed on poles; instead, they should be installed on the ground. In accordance with the relevant provisions of the **Standard ‘Design Code for Industrial and Civil 10kV and Lower Voltage Substations’, necessary installation conditions are specified to ensure the safe operation of transformers and prevent electric shock accidents. 2.2.5 Fuses are used on the high-voltage and low-voltage sides; on the high-voltage side, they serve as protection against internal faults in the transformer ； For the low-voltage side, it serves as overload protection. 2.2.6 In accordance with the relevant provisions of the technical regulations for the design of overhead distribution lines issued by the former Ministry of Water Resources and Electric Power. 2.2.7 It is mainly to prevent the safe operation of the transformer from being affected in case the cable terminal explodes, and to prevent capacitive current from arising between the cable and the transformer. 2.2.8 and 2.2.9 Box-type substations are easy to install and maintain, and their use at construction sites has been increasing in recent years. To ensure safety, during installation and use, in addition to inspecting and testing electrical equipment in accordance with the product’s technical specifications and relevant regulations, it is also necessary to properly ground the enclosure. 3 Imaginary power distribution lines and cable lines 3.1 Selection and installation of utility poles 3.1.1 To save wood, **the use of wooden poles and wooden crossarms is not recommended. However, at construction sites in mountainous areas, it is difficult to transport concrete poles from other places; to facilitate construction, local materials such as wooden poles and wooden crossbeams can be used. 3.1.2.2 This requirement is in place to ensure the quality of pole foundations; in some areas, accidents such as bent poles or even fallen poles have occurred due to poor compaction of the backfill soil. Based on the experience in some areas, compacting once for every 500 mm of fill is sufficient and meets the quality requirements. The anti-settlement foundation refers to the soil accumulation around the pit base after the utility poles are erected. The purpose of adding soil is to prevent the backfilled soil from sinking, which could cause the soil around the utility pole to collapse and affect the stability of its foundation. Based on experience in some areas, it is necessary to install soil retention platforms. 3.1.2.3 The burial depth of utility poles is generally based on 1/6 of the pole’s height. This clause sets out different requirements based on the length of the utility poles; when the design does not specify otherwise, the data provided in this clause may be used. 3.1.2.5 For poles equipped with transformer platforms, an embedding depth of 2m is considered sufficient to ensure safety based on experience. 3.1.3.2 The contents of this clause represent the general rules for distribution lines, and no issues have been encountered as all areas have followed these provisions. 3.1.3.3 This clause is formulated on the basis of summarizing construction experiences from various locations, with the aim of ensuring that the tension rods are subjected to proper stress and thus fulfill their intended function. 3.1.3.4 When the strain conductor passes through between the conductors, it is possible that the shaking strain conductor may come into contact with the conductors, leading to accidents; therefore, it is specified that insulators should be installed when the strain conductor passes through the conductors. The height should exceed what a human hand can reach, hence it is specified at 2.5m. 3.2 Line Installation 3.2.1 The selection of the route and pole locations is a fundamental aspect of line construction; improper selection can threaten the safe operation of the lines and hinder the proper progress of construction. Therefore, based on past experience, several basic requirements are outlined in this section. 3.2.2 At the construction site, there is frequent human activity and a concentration of large machinery, which increases the risk of electric shock accidents. To ensure the safety of personnel and equipment, insulated wires should be used when working in this area. 3.2.3 The construction site is crowded with people and sees frequent traffic of vehicles; therefore, this section adopts the provisions in the **standards regarding the cross-sectional area of overhead line conductors in densely populated areas. Sections 3.2.4–3.2.7 and 3.2.9, 3.2.10 all refer to the relevant provisions of the **standard \"Code for Construction and Acceptance of Electrical Installation Projects – Overhead Distribution Lines of 10 kV and Below\". 3.2.8 The installation curve tables are prepared based on different regions and climate conditions in our country, by using various types of conductors and different cross-sectional areas for them. 3.3 Cable Laying 3.3.1 The construction site is frequently excavated and backfilled; to prevent the cables from being damaged or broken, they should be laid along roadsides or the edges of buildings. To facilitate their identification, maintenance, and protection, markers indicating the path of the cables should be installed along their route. 3.3.2 High-voltage cables, as well as low-voltage cables in areas subject to mechanical damage and frequent traffic from vehicles and people, should be buried at a depth of 0.7 m or more; under normal circumstances, a depth of 0.2 m is sufficient. Sections 3.3.3 and 3.3.5 shall refer to the relevant provisions of the **Standard: Code for Construction and Acceptance of Electrical Installation Projects – Cable Lines Section**. 3.3.4 The installation height of cables is specified to avoid interfering with the normal progress of construction work and the movement of personnel. The construction quality of low-voltage cable terminations is generally poor, and they are prone to water ingress and arcing; therefore, higher standards are required. 4 Grounding Protection and Lightning Protection 4.1 Grounding Protection 4.1.1 In a TN-S grounding system, the PE wire does not carry load current under normal conditions; therefore, the PE wire and the equipment’s casing are not electrified under normal circumstances. They only acquire a potential when a grounding fault occurs. Hence, this system is relatively safe to use at construction sites. However, in some construction sites, the power supply area is large and dispersed; it is somewhat difficult to run 5 wires from the power source, and the long distances and high impedance pose problems when using the TN-S system. Therefore, the TT system should be adopted, with the enclosures of electrical equipment connected directly to the grounding electrode. 4.1.2 In accordance with the relevant provisions of the **Standard ‘Code for Design of Grounding in Industrial and Civil Electrical Installations’, it is determined based on the level of electricity usage at construction sites in China. The metal casing of electrical equipment, as well as the metal frames connected to such equipment, must be reliably connected to the PE protection wire. This is done to prevent the casing from becoming charged in the event of insulation failure of the electrical equipment, thereby avoiding threats to human safety; hence, grounding measures are employed. 4.1.3.1 The purpose of repeated grounding is to reduce the voltage to ground when the equipment enclosure is charged. 4.1.3.2 Provisions made, in light of the characteristics of the construction site, to improve the reliability of the protective neutral wire and prevent errors in its connection or breaks. 4.1.3.3 PE conductor cross-section determined based on thermal stability requirements. 4.1.3.4 The minimum cross-sectional area of the protective neutral wire for mobile or hand-held electric tools, as determined in accordance with the relevant provisions of the **Standard ‘Safety Technical Regulations for the Management, Use, Inspection, and Maintenance of Handheld Electric Tools’**. 4.1.4 To prevent all the following devices from losing protection due to poor contact or disconnection of the protective ground wire or protective neutral wire of a particular device, it is specified that grounding must be done in parallel only, and not in series. 4.1.8 Using natural grounding electrodes facilitates construction, ensures reliable grounding, and saves materials. Operational experience has shown that in areas with low soil resistivity, it is possible to avoid the need for artificial grounding electrodes when natural ones are utilized. 4.2 Lightning Protection 4.2.2 It is determined in accordance with the requirements of the **Standards for Safety of Tower Cranes and Code for Design of Lightning Protection in Buildings**, taking into account the height of construction machinery and structures at the construction site. 5 Common Electrical Equipment 5.2 Distribution Boxes and Switch Boxes 5.2.1–5.2.3 specify the requirements for the environment surrounding distribution boxes and switch boxes, to facilitate wiring, cable connections, and maintenance, thereby ensuring safe and reliable operation. 5.2.5 Easy to use, maintain, and repair. 5.2.6 Separate switches are provided for lighting and power supply; this is to ensure the safety of lighting circuits and to prevent lighting from being affected by faults in the power supply lines. 5.4 Mobile power tools and hand-held power tools 5.4.3 This requirement shall be met using a three-core rubber-sheathed flexible cable. 5.4.4 To prevent a malfunction in one power tool from affecting the use of other power tools, as well as to facilitate use, inspection, and maintenance. 5.4.7 Prevent sudden rotation of powered tools to avoid accidents. 5.4.8 Complies with the relevant provisions of the **Standard ‘Safety Technical Regulations for the Management, Use, Inspection, and Maintenance of Handheld Electric Tools’. 5.4.12 Prevent accidental electric shock. 5.5 Welding Machines 5.5.1 Centralized power supply is necessary for easier management, to prevent accidents, and to ensure proper construction practices. 5.5.2～5.5.8 The requirements for the location of welding machines, as well as the regulations regarding grounding, are specified in accordance with the needs for moisture protection, fire prevention, and electric shock prevention. 5.5.9 The secondary lead of the welding machine is often dragged along the ground as the construction site changes, and the conditions at the construction site are poor, which can easily damage the welding wire; therefore, it is necessary to use high-quality rubber-sheathed flexible cables. 5.6 Cranes 5.6.4 Equipment and miscellaneous items stored near the tracks can interfere with the retraction and extension of cables, and they may also damage the cables, thereby leading to accidents; hence this requirement is stipulated. 5.6.6 Medium and small cranes are generally operated using button switches on the ground, with a power switch installed on or near the crane to allow for immediate power disconnection in case of an accident. 5.6.8 Making arbitrary changes to electrical equipment and wiring methods can affect the operator’s familiarity with the equipment, increasing the risk of operational errors. 5.6.9 Prevent maintenance and operation of electrical equipment from affecting the operation of other related specialties, as well as personal safety and equipment safety. Inspecting equipment during lifting processes interferes with the lifting operation and can easily lead to lifting accidents. 5.6.11 Improve the reliability of grounding protection and ensure the required grounding resistance. 6 Special Environments 6.1 Flammable and Explosive Environments 6.1.3–6.1.5 The use of explosion-proof equipment and the implementation of explosion-proof measures are aimed at preventing the generation of sparks and reducing the occurrence of fires and explosions. 6.1.6 In accordance with the provisions of the **Standards: Code for Design of Electrical Installations in Explosive and Fire-Hazardous Environments** and **Code for Construction and Acceptance of Electrical Installations in Explosive and Fire-Hazardous Areas for Electrical Installation Projects**. 6.2 Corrosive Environment 6.2.1 The so-called dominant wind direction refers to the single wind direction with the highest frequency of occurrence within a year. Prevent corrosive substances from damaging electrical equipment, thereby avoiding a reduction in insulation or its destruction. 6.2.2 The principles for determining the corrosion protection distance take into account both staying away from sources of corrosive substances and minimizing line losses as well as saving land use. The definitions of Class I corrosion environments and Class II corrosion environments are provided in the \"Technical Regulations for Electrical Design in Corrosive Environments of Chemical Enterprises\". 6.2.5 Due to the poor chemical resistance of wood, cement poles and angle steel crossarms are used. There is years of operational experience in various regions using higher voltage levels to enhance insulation. 6.2.6 All-plastic cables (cables with plastic insulation and plastic sheathing) possess excellent electrical properties and reliable corrosion resistance; Chinese chemical enterprises have many years of experience in using such cables in operational settings. The method of installing insulated wires in conduits is complicated to implement; it leads to easy corrosion and moisture damage, results in poor electrical insulation properties, and incurs high operating costs. With the cable trench installation method, cables are prone to corrosion and water damage within the trenches, as well as mechanical damage, which shortens their service life. Hence, these regulations were established. 6.2.7 Reliable measures for safe power supply and use in corrosive environments. Improve the reliability of joint connections. 6.2.8 Cable entry and exit points for distribution boxes, control boxes, etc., in corrosive environments should be equipped with cable sealing sleeves; manufacturers are able to supply these as part of their products. During construction, attention must be paid to implementing proper sealing and anti-corrosion measures at these cable entry and exit points. 6.2.9 Copper-core wires have good corrosion resistance, but their cost is high; therefore, they are used only in highly corrosive environments. 6.3 Particularly humid environments An environment is considered humid when its relative humidity is consistently above 75%, while it is regarded as particularly humid when the relative humidity is close to 100%. When performing electrical work in particularly humid environments, it is necessary to follow the five most basic principles outlined in this section. Special care must be taken when using mobile or portable power tools; installing leakage protectors, wearing insulating boots, and working on an insulating platform are all effective measures to ensure safety. 7 Lighting 7.0.2 Refer to the relevant provisions in the section on electrical lighting installations of the national standard \"Code for Construction and Acceptance of Electrical Installation Projects\". The hanging height of the lighting fixtures is determined based on the actual conditions at the construction site. 7.0.4 Some requirements established to prevent a decrease in insulation or insulation failure. 7.0.5 General requirements for protection against electric shock. 7.0.6 Refer to the relevant provisions in the Electrical Lighting Devices section of the national standard \"Code for Construction and Acceptance of Electrical Installation Projects\". 7.0.7 Prevent the metal containers or pipes from becoming electrified in the event of insulation failure on the primary side of the track light transformer. 7.0.8 This is specified to ensure that maintenance personnel are not at risk of electric shock when servicing distribution panels, switchgear, and busbars, while also taking into account the need to avoid disruptions to power supply and consumption. 7.0.9 Fire protection requirements derived from operational experience. 8 Safety Technology Management 8.0.1～8.0.3 Strengthening the management of power supply and consumption, as well as the necessary organizational and technical measures to ensure safe power supply and consumption. 8.0.4 Necessary qualifications for operators and maintenance personnel of construction electricity. 8.0.8, 8.0.9 To ensure the personal safety of the personnel on duty as well as the safety of the equipment during operation, maintenance, and other activities, it is necessary to have certain essential safety equipment and measures in place. 8.0.11 Severe weather can lead to accidents such as pole collapse, wire breaks, damage to electrical equipment, and reduced insulation; therefore, inspections and surveillance should be intensified. To ensure the safety of inspectors, proper protection should be in place during inspections. 8.0.12 New equipment and equipment that has been overhauled shall undergo a 72-hour trial run; it can be put into formal operation only after passing this test. 8.0.13 specifies the cleaning and maintenance cycles for power supply and consumption facilities. 8.0.14 and 8.0.15 refer to the provisions of the Ministry of Energy’s \"Safety Regulations for the Electric Power Industry\" (Electrical Part for Power Plants and Substations). 8.0.16.1 To strengthen the management of electrical load. 8.0.16.2 To ensure the safety of maintenance personnel, a supervisor must be assigned. 8.0.16.3 Removing it promptly after use ensures safety and prevents the loss of equipment and supplies. 8.0.16.4 Electrical work is a type of special task that requires training; one must pass relevant examinations before being allowed to carry out electrical work properly, as otherwise accidents are likely to occur. Generally, those who have not taken the exam are prohibited from tampering with electrical equipment. 8.0.16.5 is intended to prevent electric shock and misuse of power supply facilities.
Announcement by the Ministry of Construction of the People’s Republic of China, No. 322: Announcement by the Ministry of Construction on the Issuance of the Industry Standard “Technical Specifications for Safety in Temporary Electricity Use at Construction Sites”. The “Technical Specifications for Safety in Temporary Electricity Use at Construction Sites” are hereby approved as an industry standard, with the code JGJ 46-2005; it shall come into effect as of July 1, 2005. Among them, clauses 1.0.3, 3.1.4, 3.1.5, 3.3.4, 5.1.1, 5.1.2, 5.1.10, 5.3.2, 5.4.7, 6.1.6, 6.1.8, 6.2.3, 6.2.7, 7.2.1, 7.2.3, 8.1.3, 8.1.11, 8.2.10, 8.2.11, 8.2.15, 8.3.4, 9.7.3, 10.2.2, 10.2.5, and 10.3.11 are mandatory provisions that must be strictly enforced. The original industry standard, \"Technical Code for Safety of Temporary Electricity Use at Construction Sites\" JGJ 46-88, is also repealed simultaneously. This standard was organized by the Standard and Quota Research Institute of the Ministry of Construction and published by China Architecture & Building Press. Preface In accordance with the requirements of Document Jianbiao [2001] No. 16 issued by the Ministry of Construction, the standard drafting team revised this specification after conducting extensive investigations and research, carefully summarizing practical experience, referring to relevant international standards, and seeking wide-ranging opinions. The main technical contents of this specification are: 1. General provisions ； 2. Terms, codes ； 3. Temporary power usage management ； 4. Protection of external electrical lines and electrical equipment ； 5. Add provisions regarding the installation of the protective neutral wire in zero-grounding protection systems, as well as rules for the insulation colors of phase wires, working neutral wires, and protective neutral wires; also include rules for determining the lightning protection area using the rolling ball method ； 6. Provisions for adding lighting in the power distribution room ； 7. Add provisions regarding the selection and installation methods for cable lines, as well as guidelines for the use of five-core cables ； 8. Additional provisions regarding the structure of distribution boxes and switch boxes, as well as the electrical equipment specified and wiring methods ； 9. Requirements to add secondary electric shock protection devices to welding machines, to install controllers for devices that are used frequently, and to conduct insulation checks on handheld power tools ； 10. Add provisions regarding the use of safety isolation transformers, as well as rules on the safe distance between lighting fixtures and flammable and explosive materials and the protective measures to be taken. The Ministry of Construction is responsible for the management of these specifications and for interpreting the mandatory provisions, while the organizing unit is responsible for explaining the specific technical content. Principal drafting unit of this standard: Shenyang Jianzhu University (Address: Hunnan New Area, Shenyang City, Postal Code: 110000)
Contributing units to this standard: Building Safety Branch of China Construction Industry Association, Shanghai Construction Safety Association, Shandong Provincial Construction Safety Supervision Station, Jiangsu Provincial Building Safety and Equipment Management Association, Anhui Provincial Construction Industry Safety Association, Yunnan Provincial Construction Project Safety Supervision Station, Wuhan Urban and Rural Work Safety Management Station, Shaanxi Provincial Construction Project Quality and Safety Supervision Station, Yantai Construction Safety Supervision Station, Liaoning Provincial Department of Construction, Fushun Municipal Engineering Quality and Safety Supervision Station
Main drafters of this standard: Xu Rongjie, Qin Chunfang, Kong Jinqiang, Li Yin, Wu Xiuli, Gu Jiansheng, Liu Shicai, Zhang Ming, Pu Yufeng, Cao Xianping, Bian Erlun, Wang Xiaobo, Liu Shaofei, Li Changkai, Bai Bo
Table of Contents
1 General Provisions
2 Terms and Codes
2.1 Terms
2.2 Codes
3 Management of Temporary Electricity Use
3.1 Design for Temporary Electricity Use
3.2 Electricians and Personnel Using Electricity
3.3 Safety Technical Records
4 Protection of External Power Lines and Electrical Equipment
4.1 Protection of External Power Lines
4.2 Protection of Electrical Equipment
5 Grounding and Lightning Protection
5.1 General Provisions
5.2 Protective Zero Connection
5.3 Grounding and Ground Resistance
5.4 Lightning Protection
6 Distribution Rooms and Self-Provided Power Sources
6.1 Distribution Rooms
6.2 230/400V Self-Provided Generator Sets
7 Distribution Lines
7.1 Overhead Lines
7.2 Cable Lines
7.3 Indoor Wiring
8 Distribution Boxes and Switch Boxes
8.1 Installation of Distribution Boxes and Switch Boxes
8.2 Selection of Electrical Devices
8.3 Use and Maintenance
9 Electric Construction Machinery and Handheld Electric Tools
9.1 General Provisions
9.2 Lifting Machinery
9.3 Pile Driving Machinery
9.4 Earthmoving Machinery
9.5 Welding Machinery
9.6 Handheld Electric Tools
9.7 Other Electric Construction Machinery
10 Lighting
10.1 General Provisions
10.2 Lighting Power Supply
10.3 Lighting Fixtures
Appendix A Average Annual Number of Thunderstorm Days in China
Appendix B Ball-rolling Method
Appendix C Motor Load Lines and Selection of Electrical Devices
Explanation of Terms Used in This Standard
Explanations of Articles
1 General Provisions
1.0.1 This standard is formulated to implement laws and regulations on work safety, ensure electrical safety at construction sites, prevent electric shock and electrical fires, and promote the development of the construction industry. 1.0.2 These specifications apply to the design, installation, use, maintenance, and demolition of low-voltage power systems with a 220/380V three-phase four-wire system and directly grounded neutral point, used in temporary electrical installations at construction sites for new, renovated, and expanded industrial and civil buildings as well as municipal infrastructure projects. 1.0.3 A 220/380V three-phase four-wire low-voltage power system with the neutral point directly grounded, designed specifically for temporary electrical use at construction sites, must comply with the following requirements: 1 A three-level power distribution system shall be employed ； 2 Adopt a TN-S neutral protection system ； 3 A two-stage leakage protection system is adopted. 1.0.4 For temporary power use at construction sites, in addition to complying with the provisions of these specifications, it is also necessary to meet the requirements of **current relevant mandatory standards. 2 Terms and Codes 2.1 Terms 2.1.1 Low voltage Voltage with an AC rated voltage of 1 kV or less. 2.1.2 High voltage: A voltage with an AC rated voltage of 1 kV or more. 2.1.3 External circuit: Electrical circuits other than those in the distribution network for temporary power supply at the construction site. 2.1.4 Construction sites with electrostatic fields These are construction sites where harmful static electricity can be generated as a result of friction, compression, induction, and poor grounding, posing risks to both humans and the environment. 2.1.5 Source of powerful electromagnetic waves: An electromagnetic radiator whose radiant waves can induce harmful voltages with respect to the ground in the mechanical equipment at the construction site. 2.1.6 Ground connection A part of the equipment is used to establish a conductive path to the earth. 2.1.7 Working ground connection A grounding connection that is necessary for circuits or equipment to meet their operational requirements, such as the grounding of the low-voltage neutral point of transformers and the neutral point of generators. 2.1.8 Iterative ground connection: A grounding method in which one or more points on the equipment’s grounding wire are reconnected to the earth through grounding devices. 2.1.9 Earth lead A metal conductor that is buried in the ground and in direct contact with the earth. 2.1.10 Manual grounding A grounding electrode that is manually buried in the ground. 2.1.11 Natural grounding: Components that have been buried in the ground prior to construction and can be used as grounding elements, such as the rebar structure of reinforced concrete foundations, metal well pipes, and metal pipelines (other than those for gas). 2.1.12 Ground line: A metal conductor that connects the metal structure of the equipment to the grounding electrode (including the connection bolts). 2.1.13 Grounding device: The combination of the grounding electrode and the grounding wire. 2.1.14 Ground resistance: The resistance of the grounding system relative to the ground. It is the sum of the resistance of the grounding wire, the resistance of the grounding electrode, the contact resistance between the grounding electrode and the soil, and the stray resistance in the soil. The ground resistance can have an approximate value determined by calculation or measurement; this value equals the ratio of the voltage of the grounding device with respect to the ground to the current flowing into the ground through that grounding device. 2.1.15 Power frequency ground resistance: The ground resistance determined based on the power frequency current that flows into the ground through the grounding device. 2.1.16 Shock ground resistance: The ground resistance determined based on the impulse current (simulating lightning current) that flows into the ground through the grounding system. 2.1.17 Electrical connection: A connection that provides a direct electrical path between conductors (with contact resistance close to zero). 2.1.18 Live-part: A conductor or conductive part that is energized during normal operation. It includes the neutral conductor (neutral wire), but does not include the protective conductor (protective neutral wire or protective line). Conventionally, it also does not include wires (conductors) in which the working neutral wire and the protective neutral wire are combined. 2.1.19 Exposed conductive part: A touchable conductive part of an electrical equipment. It is not charged under normal conditions, but it may become charged in the event of a fault. 2.1.20 Electric shock: Current flowing through a human body or an animal’s body, causing pathophysiological effects. 2.1.21 Direct contact: Contact between the human body or livestock and live parts. 2.1.22 Indirect contact: Contact between the human body, livestock, and exposed conductive parts that become charged under fault conditions. 2.1.23 Distribution box: A device specifically used for distributing electricity, including the main distribution box and the distribution boxes; unless otherwise specified, the main distribution box and the distribution boxes are collectively referred to as distribution boxes. 2.1.24 Switch box: A general term for the final level of power distribution equipment; it can also serve as a control device for electrical equipment. 2.1.25 Isolating transformer: A transformer in which the input winding and the output winding are electrically isolated from each other, used to prevent the danger posed by accidental simultaneous contact with live parts (or metal components that may become live due to damaged electrical insulation) and the ground. 2.1.26 Safety isolating transformer: An isolating transformer that supplies power to safely low-voltage circuits. Its input winding and output winding are electrically separated by insulation equivalent to double insulation or reinforced insulation. It is designed specifically to provide a safe extremely low voltage for distribution circuits, tools, or other equipment. 2.2 Codes 2.2.1 DK——Power isolation switch ； 2.2.2 H——Lighting fixture ； 2.2.3 L1, L2, L3 —— the three phase wires of a three-phase circuit ； 2.2.4 M——Electric motor ； 2.2.5 N——Neutral point, neutral wire, working neutral wire ； 2.2.6 NPE —— A grounding wire with both neutral and protective functions, also known as protective neutral wire ； 2.2.7 PE — Protection neutral wire, protective wire ； 2.2.8 RCD — Residual current device, leakage circuit breaker ； 2.2.9 T——Transformer ； 2.2.10 TN – A neutral grounding protection system in which the exposed conductive parts of electrical equipment are connected to the ground through the neutral wire, when the power supply’s neutral point is directly grounded ； 2.2.11 TN-C —— A neutral protection system in which the working neutral and the protective neutral are combined ； 2.2.12 TN-C-S —— a neutral protection system in which the working neutral and the first part of the protective neutral are combined, while the latter part is separated ； 2.2.13 PN-S —— A neutral protection system in which the working neutral and the protective neutral are separated ； 2.2.14 TT – A grounding protection system in which the power supply neutral point is directly grounded, and the exposed conductive parts of electrical equipment are also directly grounded; the grounding point for electrical equipment is separate from the grounding point of the power supply neutral point ； 2.2.15 W——Welding machine. 3 Management of Temporary Electricity Use 3.1 Organizational Design for Temporary Electricity Use 3.1.1 When there are 5 or more temporary electricity devices at a construction site, or when the total capacity of these devices is 50 kW or more, an organizational design for electricity use must be prepared. 3.1.2 The temporary electrical power supply plan for the construction site shall include the following contents: 1 Site survey ； 2 Determine the locations of the power supply inlet, substation or distribution room, distribution equipment, electrical appliances, as well as the route of the electrical circuits ； 3 Perform load calculation ； 4 Select the transformer ； 5 Design of the power distribution system: 1) Design the power distribution lines, selecting wires or cables ； 2) Design the power distribution apparatus and select electrical equipment ； 3) Design the grounding device ； 4) Draw drawings for temporary power supply projects, which mainly include the general layout plan of the power supply system, the layout diagram of the distribution equipment, the wiring diagram of the distribution system, and the design diagram of the grounding system. 6 Design of lightning protection devices ； 7 Determine protective measures ； 8 Formulate safety measures for electrical use and electrical fire prevention measures. 3.1.3 Drawings for temporary power supply projects shall be prepared separately, and such projects shall be constructed in accordance with those drawings. 3.1.4 When preparing a design for temporary power use or making changes to it, the \"preparation, review, and approval\" procedures must be followed. It shall be prepared by electrical engineering technicians, reviewed by the relevant departments, and approved by the technical director of an enterprise with legal person status before implementation. Relevant drawing materials should be added when modifying the electrical design. 3.1.5 Temporary electrical installations must be jointly inspected and approved by the departments responsible for their preparation and review, as well as by the user unit; they can only be put into use after passing such inspection. 3.1.6 For construction sites where the number of temporary electrical equipment is 5 or less and the total capacity of such equipment is 50 kW or less, safety measures for electrical use and electrical fire prevention must be established, and these measures must comply with the provisions of paragraphs 3.1.4 and 3.1.5 of this standard. 3.2 Electricians and persons using electricity 3.2.1 Electricians must pass assessments in accordance with **current standards before they can work with a valid certificate ； Other electrical workers must undergo relevant training and technical briefings, and only after passing the assessments can they start working. 3.2.2 The installation, inspection, maintenance, or removal of temporary electrical equipment and circuits must be carried out by electricians, and supervision must be provided. The electrician’s level should be appropriate to the difficulty and technical complexity of the project. 3.2.3 All users of electrical equipment must possess basic knowledge of safe electricity use as well as an understanding of the capabilities of the equipment they are using. They must also comply with the following requirements: 1 Before using electrical equipment, it is necessary to wear and use the appropriate personal protective equipment as required, and the electrical installations and protective devices must be inspected; it is strictly prohibited to operate equipment that has defects ； 2 Maintain and care for the equipment used, and report any issues promptly for resolution ； 3 The switch box of a device that is to be temporarily shut down must have its power supply isolation switch disconnected, and the door must be closed and locked ； 4 When moving electrical equipment, it must be done after the electrician cuts off the power supply and takes proper precautions. 3.3 Safety Technical Records 3.3.1 Safety technical records must be established for temporary electricity use at construction sites, and these records should include the following contents: 1 Safety documents related to the electrical installation plan ； 2 Modify the materials for the electrical design plan ； 3 Electrical Technology Briefing Materials ； 4 Electrical Engineering Inspection and Acceptance Form ； 5 Test and inspection certificates for electrical equipment and commissioning records ； 6 Record Form for Measuring Ground Resistance, Insulation Resistance, and Leakage Operation Parameters of Leakage Circuit Breakers ； 7 Regular Inspection (Review) Table ； 8 Records of electrical work installation, inspection, maintenance, and demolition. 3.3.2 The safety technical records shall be established and managed by the electrical technician in charge of the site. Among these, the “records of electrical work installation, inspection, maintenance, and demolition” can be entrusted to an electrician for management; they must be reviewed and approved by the project manager on a weekly basis, and should be archived collectively after the temporary electrical installations are removed. 3.3.3 Temporary electrical installations should be inspected regularly. During regular inspections, the ground resistance value and insulation resistance value should be rechecked. 3.3.4 Regular inspections of temporary electrical installations should be carried out by section and in phases; any safety hazards must be addressed promptly, and re-inspection and acceptance procedures must be followed. 4 Protection of External Power Lines and Electrical Equipment 4.1 Protection of External Power Lines 4.1.1 Construction projects shall not carry out work, set up temporary shelters, build living facilities, or stack components, tools, materials, and other debris directly below external overhead power lines. 4.1.2 The minimum safe operating distance between the perimeter of the construction in progress (including scaffolding) and the edge of the external overhead power lines shall comply with the requirements specified in Table 4.1.2. Table 4.1.2 Minimum safe operating distance between the perimeter of construction projects (including scaffolding) and the edge of overhead power lines. Note: The ladders for ascending and descending from the scaffolding should not be located on the side where there are external power lines. 4.1.3 When the motor vehicle lane at the construction site intersects with overhead external power lines, the minimum vertical distance between the lowest point of the overhead lines and the road surface shall comply with the requirements specified in Table 4.1.3. Table 4.1.3 Minimum vertical distance when motor vehicle lanes and overhead lines intersect at the construction site 4.1.4 Cranes are strictly prohibited from operating above unprotected external overhead power lines. When lifting operations are carried out near external overhead power lines, the minimum safe distance between any part of the crane or the edge of the load, at its maximum tilt, and the edge of the overhead lines shall comply with the requirements specified in Table 4.1.4. Table 4.1.4 Minimum safe distance between cranes and the edge of overhead lines 4.1.5 The distance between the edge of the trench dug at the construction site and the edge of the trench for buried external electrical cables must be no less than 0.5 m. 4.1.6 When the requirements specified in paragraphs 4.1.2 to 4.1.4 of these specifications cannot be met, insulation isolation measures must be taken, and prominent warning signs shall be installed. When installing protective facilities, approval from the relevant authorities is required; temporary power shutdown of the circuit or other reliable safety measures must be employed, and the work must be supervised by electrical engineering technicians and dedicated safety personnel. The safety distance between protective facilities and external power lines shall not be less than the values specified in Table 4.1.6. The protective facilities should be sturdy and stable, and the isolation protection against external electrical lines should reach IP30 level. Table 4.1.6 Minimum safe distance between protective facilities and external power lines 4.1.7 When the protective measures specified in Article 4.1.6 of these specifications cannot be implemented, it is necessary to consult with the relevant authorities and take measures such as shutting down power supply, relocating external power lines, or changing the location of the project; construction is strictly prohibited without taking such measures. 4.1.8 When digging trenches near external overhead power lines, it is necessary to take reinforcement measures in conjunction with the relevant departments to prevent the poles of these overhead lines from tilting or falling over. 4.2 Protection of electrical equipment 4.2.1 Flammable and explosive substances, sources of contamination, and corrosive agents must not be stored around electrical equipment; if such substances are present, they must be removed or protected, and the level of protection required must be appropriate to the environmental conditions. 4.2.2 The location where electrical equipment is installed should be free from object impact and mechanical damage; otherwise, protective measures should be taken. 5 Grounding and Lightning Protection 5.1 General Provisions 5.1.1 In a TN-S neutral protection system powered by a dedicated transformer at the construction site, the metal enclosures of electrical equipment must be connected to the protective neutral wire. The protective neutral wire should be derived from the working ground wire, the neutral wire on the power side of the distribution room (main distribution panel), or the neutral wire on the power side of the main leakage protector (Figure 5.1.1). Figure 5.1.1 Schematic of TN-S neutral protection system when powered by a dedicated transformer 1 – Working ground ； 2－PE wire repeated grounding ； 3 – Metal enclosures of electrical equipment (exposed conductive parts that are not normally live) ； T-Transformer 5.1.2 When the construction site shares the same power supply system as external electrical lines, the grounding and neutral connection protection of electrical equipment shall be consistent with the protection of the original system. It is not allowed to use protective zero connection for some equipment while using protective grounding for other equipment. When using the TN system for protective earthing, the working neutral wire (N wire) must pass through the main residual current device, while the protective earth wire (PE wire) must be led out from the point where the supply neutral wire is re-earthed or from the side of the main residual current device connected to the power supply, thereby forming a local TN-S earthing protection system (Figure 5.1.2). Figure 5.1.2 Schematic diagram of the protective neutral conductor in a local TN-S neutral grounding system during three-phase four-wire power supply; 1 – Repeated grounding of the NPE conductor ； 2－PE wire repeated grounding ； L1, L2, L3 – phase wires ； N – Working neutral wire ； PE – Protective neutral wire ； DK – Main power isolation switch ； RCD – Main leakage protector (a circuit breaker that provides protection against short circuits, overloads, and leakage current). 5.1.3 In a TN system with neutral grounding, no further electrical connections shall be made between the working neutral wire and the protective neutral wire via the main leakage protector. 5.1.4 In a TN neutral-grounded protection system, the PE neutral wire shall be laid separately. The repeated grounding wire must be connected to the PE wire; it is strictly prohibited to connect it to the N wire. 5.1.5 When a safety isolation transformer is used, with the primary side powered by a neutral-grounded protection system having a voltage of 50V or higher and the secondary side having a voltage of 50V or lower, the secondary side shall not be grounded; furthermore, the secondary wiring shall be protected by insulated tubes or flexible wires with rubber sheaths. When a conventional isolation transformer is used, one end of its secondary side should be grounded, and the exposed conductive parts of the transformer that are not energized under normal conditions should be connected to the protective neutral wire of the primary circuit. The above transformers shall also be equipped with protection measures to prevent direct contact with live parts. 5.1.6 In the temporary electrical power system at the construction site, it is strictly prohibited to use the ground as a phase wire or neutral wire. 5.1.7 The installation of grounding devices shall take into account the effects of seasonal changes such as soil drying or freezing, and shall comply with the provisions in Table 5.1.7; the grounding resistance value shall meet the requirements of Section 5.3 of this code throughout all four seasons. However, the impulse grounding resistance value of lightning protection devices only takes into account the effect of dry soil conditions during the thunderstorm season. Table 5.1.7 Seasonal coefficient φ values for grounding devices Note: When the ground is relatively dry, use the smaller value from the table ； In relatively humid conditions, use the higher value from the table. 5.1.8 When the material used for the PE wire is the same as that of the phase wires and the working neutral wire (N wire), its minimum cross-sectional area shall comply with the provisions in Table 5.1.8. Table 5.1.8 Relationship between the cross-sectional area of the PE wire and that of the phase wires 5.1.9 The protective neutral wire must be made of insulated wire. The PE wire connecting the distribution device and the electric machinery shall be an insulated multi-strand copper wire with a cross-sectional area of not less than 2.5 mm2. The PE wire of handheld power tools should be insulated multi-strand copper wire with a cross-sectional area of not less than 1.5 mm2. 5.1.10 Switches or fuses must not be installed on the PE conductor; it must not carry operating current, and the wire must not be disconnected. 5.1.11 The color coding of the live wires, N wire, and PE wire must comply with the following regulations: the insulation colors for the live wires L1 (A), L2 (B), and L3 (C) in order are yellow, green, and red respectively ； The insulation color of the N wire is light blue ； The insulation color of the PE wire is green/yellow. Under no circumstances shall the aforementioned color codes be mixed or used interchangeably. 5.2 Protective Earthing 5.2.1 In a TN system, the exposed conductive parts that are not live in the following electrical equipment shall be connected to earth for protection: 1 The metal casings of motors, transformers, electrical appliances, lighting fixtures, and hand-held electric tools ； 2 Metal components of the drive mechanisms in electrical equipment ； 3 Metal frames of distribution cabinets and control cabinets ； 4 Metal enclosures, frames of distribution equipment, as well as metal fences and doors located near live parts ； 5 Metal protective tubes for power lines, steel cables for wiring, bases and tracks for cranes, metal working platforms for slipform construction, etc ； 6 The metal enclosures and supports of electrical devices such as switches and capacitors installed on power line poles (towers). 5.2.2 Electrical equipment in damp or particularly harsh-condition construction sites such as fortifications, civil air defense facilities, and tunnels must be equipped with protective zero connection. 5.2.3 In TN systems, the exposed conductive parts of the following electrical equipment that are not live do not require protection grounding: 1 The metal enclosures of electrical installations with an AC voltage of 380V or less in dry rooms with poorly conductive floors such as wood or asphalt (except in cases where maintenance personnel may come into contact simultaneously with both the metal enclosure of the electrical equipment and the grounded metal parts) ； 2 Electrical measuring instruments, current transformers, and the metal enclosures of electrical appliances that are installed on the metal frames of distribution cabinets, control cabinets, and distribution boxes, and are in reliable electrical connection with them. 5.3 Grounding and Ground Resistance 5.3.1 The working ground resistance value of power transformers or generators with a single unit capacity exceeding 100 kVA, or those operating in parallel using the same grounding system and having a total capacity exceeding 100 kVA, must not be greater than 4 Ω. The working ground resistance value of power transformers or generators with a single-unit capacity of no more than 100 kVA, or those operating in parallel using the same grounding system with a total capacity of no more than 100 kVA, must not be greater than 10 Ω. In areas where the soil resistivity is greater than 1000Ω•m, when it is difficult to achieve the aforementioned grounding resistance value, the working grounding resistance can be increased to 30Ω. 5.3.2 In a TN system, in addition to being repeatedly grounded at the distribution room or main distribution panel, the protective neutral wire must also be repeatedly grounded at intermediate points and at the end of the distribution system. In TN systems, the grounding resistance value of each repeated grounding device for the protective neutral wire should not exceed 10Ω. In power systems where the allowable value for the working ground resistance is 10Ω, the equivalent resistance value of all repeated grounds should not exceed 10Ω. 5.3.3 In TN systems, it is strictly prohibited to provide additional grounding for the separately laid working neutral wire. 5.3.4 The grounding wires of each grounding device shall consist of 2 or more conductors, which make electrical connections to the grounding electrode at different points. Aluminum conductors shall not be used as grounding electrodes or underground grounding wires. For vertical grounding electrodes, angle steel, steel pipes, or plain round steel should be used; deformed steel bars must not be employed. Grounding can utilize natural grounding electrodes, but their electrical connection and thermal stability must be ensured. 5.3.5 For electrical equipment powered by mobile generators, its metal enclosure or base shall be in reliable electrical connection with the generator’s grounding device. 5.3.6 The grounding of mobile generator systems shall meet the requirements for the grounding of power transformer systems. The following situations exempt the need for additional protective grounding: 1. When a portable generator and the electrical equipment it powers are mounted on the same metal frame, and no power is supplied to other devices. 2 Electrical equipment in a quantity not exceeding 2 units may be powered by a dedicated mobile generator, provided that the distance between the power supply equipment and the electrical equipment itself is no more than 50 meters, and there is a reliable electrical connection between the metal enclosures of both types of equipment. 5.3.7 In construction sites with static electricity, grounding and leakage measures should be taken for the static electricity accumulated on mechanical equipment. The grounding resistance value of the dedicated static grounding electrode in each group should not exceed 100Ω; in areas with high soil resistivity, it should not exceed 1000Ω. 5.4 Lightning Protection 5.4.1 In areas where the soil resistivity is below 200Ω•m, it may not be necessary to install a separate lightning protection grounding system for the utility poles; however, at the overhead incoming or outgoing connections in the distribution room, the insulator feet should be connected to the grounding system of the distribution room. 5.4.2 Mechanical equipment such as cranes, jib cranes, and gantry cranes on the construction site, as well as metal structures such as steel scaffolding and structures that are under construction, shall be equipped with lightning protection devices in accordance with the provisions of Table 5.4.2 when they are located outside the protection range of the lightning arresters of the lightning protection systems of adjacent buildings, structures, and other facilities. The average annual number of thunderstorm days (d) per region in Table 5.4.2 shall be determined in accordance with Appendix A of this code. When the protection range of the lightning rod (lightning conductor) on the highest mechanical equipment can cover other equipment, and that equipment is the last to be removed from the site, those other devices do not need to be equipped with lightning protection systems. The protection area of the lightning receptor in a lightning protection system can be determined using the rolling sphere method specified in Appendix B of this code. Table 5.4.2 Requirements for installing lightning protection devices on mechanical equipment and overhead structures at construction sites 5.4.3 The lightning protection down conductors for mechanical equipment or structures can utilize the metal framework of such equipment or structures, provided that an electrical connection is ensured. 5.4.4 The length of the lightning rods (lightning conductors) on mechanical equipment should be 1–2 m. Tower cranes do not require a separate lightning rod (lightning conductor). 5.4.5 For the mechanical equipment used to install lightning rods (lightning conductors), all fixed power, control, lighting, signaling, and communication cables should preferably be laid in steel pipes. The steel pipe and the metal structure of the mechanical equipment should be electrically connected. 5.4.6 The impulse grounding resistance value of all lightning protection devices at the construction site shall not exceed 30Ω. 5.4.7 For electrical equipment installed on machinery designed for lightning protection, the PE wire connected to such equipment must also be provided with a redundant grounding connection. The redundant grounding for the electrical equipment on the same machinery and the lightning protection grounding for the machinery can share the same grounding electrode, but the grounding resistance must meet the requirements specified for redundant grounding resistance. 6 Distribution Rooms and On-site Power Supplies 6.1 Distribution Rooms 6.1.1 Distribution rooms should be located near the power source, and in areas with low levels of dust and moisture, minimal vibration, no corrosive substances, no flammable or explosive materials, and good road access. 6.1.2 The ends of the arranged distribution cabinets and control cabinets shall be electrically connected to the repeated grounding wire and the protective neutral wire. 6.1.3 The distribution room and control room shall be capable of natural ventilation, and measures shall be taken to prevent rain, snow from entering as well as animals from getting in. 6.1.4 The layout of the distribution room shall meet the following requirements: 1 The width of the operation passage on the front side of the distribution cabinets shall be no less than 1.5 m when the cabinets are arranged in a single row or in two rows back to back, and no less than 2 m when they are arranged in two rows face to face ； 2 The width of the maintenance passage behind the distribution cabinet should be no less than 0.8 m when the cabinets are arranged in a single row or face to face in two rows; it should be no less than 1.5 m when arranged back to back in two rows. In areas where there are protrusions in the building structure, the width of the passage at such locations can be reduced by 0.2 m ； 3 The maintenance access width on the side of the distribution cabinet shall be no less than 1m ； 4 The distance between the top grid of the distribution room and the ground should be no less than 3m ； 5 When a duty or maintenance room is installed inside the distribution room, the horizontal distance between the edge of this room and the distribution cabinets should be greater than 1 m, and barriers should be used for separation ； 6 When the vertical distance between the exposed busbars in the switchgear room and the ground is less than 2.5 m, barriers shall be used for isolation, and the height of the passage beneath the barriers shall be not less than 1.9 m. 7 The clear distance between the upper edge of the distribution room fence and the live parts directly above it shall be not less than 0.075 m ； 8 The upper end of the distribution device should be at a distance of not less than 0.5m from the shed ； 9 The busbars in the distribution room are painted with colored paint to indicate the phase sequence ； Based on the front side of the cabinet, its coloring shall comply with the requirements specified in Table 6.1.4 ； The fire resistance rating of the buildings and structures in the 10 distribution rooms shall be no less than grade 3; sand boxes and fire extinguishers suitable for extinguishing electrical fires shall be installed inside ； Table 6.1.4 Busbar Coloring 11 The doors of the distribution room open outward and are equipped with locks ； 12 The lighting in the distribution room is equipped with both normal lighting and emergency lighting. 6.1.5 The distribution cabinet shall be equipped with a wattmeter, as well as ammeters and voltmeters. An ammeter and a metering electricity meter must not share the same set of current transformers. 6.1.6 The distribution cabinet shall be equipped with a power isolation switch as well as protective devices against short circuits, overloads, and electric leakage. When the power isolation switch is opened, there should be a clearly visible break point. 6.1.7 The distribution cabinets shall be numbered and marked with their purpose. 6.1.8 When performing maintenance on a distribution cabinet or distribution circuit during a power outage, grounding wires should be installed, and a sign stating “Do not close switch – work in progress” should be placed. The switching on and off of electricity must be handled by a designated person. 6.1.9 The distribution room should be kept clean, and no clutter that may hinder operation and maintenance shall be stored there. 6.2 230/400V self-provided generator sets 6.2.1 The generator sets, as well as the control, power distribution, and maintenance rooms, can be installed separately ； They can be installed together provided that the electrical safety distances are maintained and the fire protection requirements are satisfied. 6.2.2 The exhaust duct of the generator set must extend outside. Fire extinguishers capable of putting out electrical fires must be installed in the generator set and its control and power distribution rooms; storage tanks for oil are strictly prohibited. 6.2.3 The power supply of the generator set must be interlocked with the external power line supply; parallel operation is strictly prohibited. 6.2.4 The generator set shall adopt a three-phase four-wire power supply system with the power source neutral point directly grounded, along with an independent TN-S neutral grounding protection system; the value of its working ground resistance shall meet the requirements specified in Article 5.3.1 of these specifications. 6.2.5 The generator control panel should be equipped with the following instruments: 1 AC voltage meter ； 2 AC ammeter ； 3 Active power meter ； 4 Electricity meter ； 5 Power Factor Table ； 6 Frequency Table ； 7 DC ammeter. 6.2.6 The generator power supply system shall be equipped with a power isolation switch as well as protective devices against short circuits, overloads, and electric leakage. When the power isolation switch is opened, there should be a clearly visible break point. 6.2.7 When generator sets are operated in parallel, a synchronization device must be installed, and power shall be supplied to the load only after the sets are synchronized. 7 Distribution Lines 7.1 Overhead Lines 7.1.1 Insulated wires must be used for overhead lines. 7.1.2 Overhead lines must be installed on dedicated utility poles; it is strictly prohibited to install them on trees, scaffolding, or other structures. 7.1.3 The selection of the cross-sectional area of overhead line conductors shall meet the following requirements: 1 The calculated load current in the conductor shall not exceed its allowable current capacity for continuous long-term operation. The voltage deviation at the end of the 2-wire circuit shall not exceed 5% of its rated voltage. 3 The cross-sectional area of the N and PE wires in three-phase four-wire systems shall be not less than 50% of the cross-sectional area of the phase wires, while the cross-sectional area of the neutral wire in single-phase systems is the same as that of the phase wire. 4 According to the mechanical strength requirements, the cross-sectional area of insulated copper wires shall be no less than 10 mm2, and that of insulated aluminum wires shall be no less than 16 mm2. 5 Within the span across railways, highways, rivers, and power lines, the cross-sectional area of the insulated copper wire shall be no less than 16 mm2. The cross-sectional area of the insulated aluminum wire shall be not less than 25 mm2. 7.1.4 Within one span of an overhead line, the number of joints per layer of conductors shall not exceed 50% of the number of conductors in that layer, and a single conductor shall have only one joint. There shall be no joints in the overhead lines within the span of railways, highways, rivers, and power lines. 7.1.5 The phase sequence of overhead lines shall comply with the following provisions: 1 When power and lighting lines are installed on the same crossarm, the phase sequence of the conductors is as follows: starting from the left side facing the load, they are L1, N, L2, L3, PE ； 2 When the power and lighting cables are installed separately on the upper crossarm at the second floor, the sequence of the wire phases is as follows: starting from the left side facing the load, on the upper crossarm, they are L1, L2, L3 ； On the lower crossarm, facing the load, they are L1 (L2, L3), N, and PE in sequence from the left. 7.1.6 The span of overhead lines shall not exceed 35 m. 7.1.7 The spacing between conductors of overhead lines shall not be less than 0.3 m, and the spacing between the two conductors near the pole shall not be less than 0.5 m. 7.1.8 The minimum vertical distance between the crossarms of overhead lines shall not be less than the values specified in Table 7.1.8-1 ； The crossarm should be made of angle steel or square timber; for low-voltage iron crossarms, angle steel should be selected in accordance with Table 7.1.8-2, while the cross-sectional dimensions of square timber crossarms should be 80mm×80mm ； The length of the crossarm shall be selected according to Table 7.1.8-3. Table 7.1.8-1 Minimum vertical distance between crossarms (m) Table 7.1.8-2 Selection of angle steel for low-voltage iron crossarms Table 7.1.8-3 Selection of crossarm length 7.1.9 The distance between overhead lines and adjacent lines or fixed objects shall comply with the provisions in Table 7.1.9. 7.1.10 For idle lines, reinforced concrete poles or wooden poles are preferred. Reinforced concrete poles must not have exposed rebar, cracks wider than 0.4 mm, or twisting ； The wooden pole must not be rotten, and its diameter at the top should not be less than 140 mm. Table 7.1.9 Distance between overhead lines and adjacent lines or fixed objects 7.1.11 The burial depth of utility poles should be 1/10 of the pole’s length plus 0.6 m; the backfill soil should be compacted in layers. In soft soil, it is advisable to increase the burial depth or use clamps and other means for reinforcement. 7.1.12 For straight poles and poles with angles of 15° or less, a single crossarm with a single insulator may be used; however, when crossing vehicle lanes, a single crossarm with two insulators should be employed ； For angle rods between 15° and 45°, double cross-arms with double insulators should be used ； For corner poles at an angle of 45° or more, cross arms should be used. 7.1.13 Insulators for overhead lines shall be selected in accordance with the following principles: 1. Pin-type insulators shall be used for straight poles ； 2. The tension poles use butterfly insulators. 7.1.14 The guy wires for utility poles should consist of no fewer than 3 strands of galvanized steel wire with a diameter of D4.0mm. The angle between the tie rod and the electric pole should be between 30° and 45°. The burial depth of the tie wire shall not be less than 1m. If the pole tie passes between the conductors, a tie insulator should be installed at a height of 2.5 m above the ground. 7.1.15 When it is not possible to install guy wires due to constraints imposed by the surface conditions, struts can be used as a substitute for guy wires. The burial depth of these struts must be at least 0.8 m, and their bases should be supported by a base plate or stones. The angle between the strut and the electric pole should be 30°. 7.1.16 The service conductor shall have no joints within the span, and the height of the incoming conductor above the ground shall not be less than 2.5 m. The minimum cross-sectional area of the service drop cable shall comply with the requirements specified in Table 7.1.16-1. The distance between the conductors of the power receiving line and between them and adjacent lines shall meet the requirements of Table 7.1.16-2. Table 7.1.16-1 Minimum cross-section of service conductors Table 7.1.16-2 Spacing between service conductors and adjacent lines 7.1.17 Overhead lines must be equipped with short-circuit protection. When fuses are used for short-circuit protection, the rated current of their fusing elements should not exceed 1.5 times the allowable current-carrying capacity of exposed insulated wires under continuous long-term loading. When a circuit breaker is used for short-circuit protection, the setting value of its instantaneous overcurrent trip device should be less than the single-phase short-circuit current at the end of the circuit. 7.1.18 Overload protection must be provided for overhead lines. When fuses or circuit breakers are used for overload protection, the allowable current-carrying capacity of insulated wires under continuous long-term loading should not be less than 1.25 times the rated current of the fuse element or the setting value of the long-time delay overcurrent trip device of the circuit breaker. 7.2 Cable Lines 7.2.1 The cable must contain all the working conductors as well as the conductors used as protective neutral or protective wires. Cable lines that require three-phase four-wire power distribution must use five-core cables. A five-core cable must include insulating conductors in light blue and green/yellow. The light blue core wire must be used as the N wire ； Green/yellow dual-color core wires must be used as PE wires; mixing them is strictly prohibited. 7.2.2 The selection of the cable cross-section shall comply with the provisions of paragraphs 1, 2, and 3 of Article 7.1.3 of these specifications, and shall be determined based on its allowable current-carrying capacity under long-term continuous loading and the allowable voltage deviation. 7.2.3 Cable lines shall be laid underground or overhead; it is strictly prohibited to lay them exposed on the ground, and mechanical damage as well as medium corrosion shall be avoided. Orientation markers should be provided for buried cable routes. 7.2.4 The cable type should be selected based on the installation method and environmental conditions. Armored cables are recommended for underground installation ； When using unarmored cables, they should be waterproof and resistant to corrosion. Unarmored cables are preferred for overhead installation. 7.2.5 The depth at which cables are buried directly in the ground should not be less than 0.7 m. Fine sand with a thickness of not less than 50 mm should be spread evenly around the cables on their upper, lower, left, and right sides, after which a hard protective layer such as bricks or concrete slabs should be applied. 7.2.6 For buried cables passing through buildings, structures, roads, areas prone to mechanical damage, and sports venues, as well as from a height of 2.0 m above the ground to a depth of 0.2 m underground, protective sleeves must be installed; the inner diameter of these protective sleeves shall be no less than 1.5 times the outer diameter of the cable. 7.2.7 The parallel distance between buried cables and external electrical cables as well as ducts in their vicinity shall not be less than 2 m, while the crossing distance shall not be less than 1 m. 7.2.8 The joints of buried cables shall be located in junction boxes on the ground; these junction boxes must be waterproof, dustproof, and protected from mechanical damage, and they should be placed away from areas that are prone to fire, explosion, or corrosion. 7.2.9 Aerial cables shall be laid along utility poles, supports, or walls and secured using insulators. The binding wires must be insulated, and the spacing between fixing points shall be such that the cable can withstand the load resulting from its own weight. The laying height shall comply with the requirements for the laying height of aerial lines specified in Section 7.1 of these specifications; however, when laid along a wall, the maximum sag distance from the ground shall not be less than 2.0 m. Aerial cables must never be laid along scaffolding, trees, or other structures. 7.2.10 Cable lines within under-construction projects must be introduced by burying the cables underground; it is strictly prohibited to introduce them through scaffolding. When cables are installed vertically, vertical shafts and vertical tunnels in the construction site should be made full use of, and the installation should be carried out as close as possible to the center of electrical load; there must be at least one fixing point per floor. When cables are laid horizontally, they should be firmly fixed along walls or doorways, with the maximum sag distance from the ground not being less than 2.0 m. For decoration and renovation projects or other special phases, a separate construction power usage plan should be prepared. The power cable can be laid along wall corners or the floor, but measures must be taken to protect it from mechanical damage and electrical hazards. 7.2.11 Cable circuits must be equipped with short-circuit protection and overload protection. The selection of these protective devices and cables shall comply with the requirements of Articles 7.1.17 and 7.1.18 of this specification. 7.3 Indoor Wiring 7.3.1 Indoor wiring must use insulated wires or cables. 7.3.2 Indoor wiring shall be installed using insulator posts, porcelain (plastic) clamps, insulated grooves, conduits, or steel cables, depending on the type of wiring. In humid areas or when installed underground, non-cable wiring must be laid within pipes, and the pipe ends and joints must be sealed ； When metal pipes are used for installation, they must be equipotentially connected and must also be connected to the PE wire. 7.3.3 The height of indoor exposed main cables that are not buried above the ground shall not be less than 2.5 m. 7.3.4 The outdoor end of the overhead service entrance wire shall be fixed using insulators; it shall be protected by pipes where it passes through walls, shall be at a height of not less than 2.5 m above the ground, and rain protection measures shall be taken. 7.3.5 The cross-sectional area of the wires or cables used for indoor wiring shall be determined based on the calculated load of the electrical equipment or circuits; however, the cross-sectional area of copper wires shall not be less than 1.5 mm2, and that of aluminum wires shall not be less than 2.5 mm2. 7.3.6 The spacing between hangers for cable wiring should not exceed 12 m. When using ceramic clamps to secure wires, the distance between wires should not be less than 35 mm, and the distance between ceramic clamps should not be greater than 800 mm ； When using porcelain insulators to fix wires, the distance between wires should not be less than 100 mm, and the distance between porcelain insulators should not exceed 1.5 m ； When using sheathed insulated wires or cables, they can be directly laid on steel cables. 7.3.7 Indoor wiring must be equipped with short-circuit protection and overload protection. The selection of devices for short-circuit and overload protection, as well as the insulated wires and cables, shall comply with the requirements of Articles 7.1.17 and 7.1.18 of this specification. For insulated conductor circuits laid in conduits, the rated current of the fuse used for short-circuit protection shall not be greater than 2.5 times the allowable current-carrying capacity of the insulated conductors under long-term continuous loading. 8 Distribution Boxes and Switch Boxes 8.1 Installation of Distribution Boxes and Switch Boxes 8.1.1 The distribution system should be equipped with distribution cabinets or main distribution boxes, sub-distribution boxes, and switch boxes, to implement a three-level distribution system. The power distribution system should ensure balanced three-phase loads. Single-phase electrical equipment rated at 220V or 380V should be connected to a 220/380V three-phase four-wire system ； When the current in a single-phase lighting circuit exceeds 30A, it is advisable to use a 220/380V three-phase four-wire power supply. The installation of indoor distribution cabinets shall comply with the provisions of Section 6.1 of these specifications. 8.1.2 Several distribution panels can be installed below the main power distribution panel ； Several switch boxes can be installed below the distribution box. The main power distribution box should be located in an area close to the power source, while the sub-distribution boxes should be placed in areas where electrical equipment or loads are concentrated. The distance between a sub-distribution box and a switch box should not exceed 30 meters, and the horizontal distance between a switch box and the fixed electrical equipment it controls should not exceed 3 meters. 8.1.3 Each electrical device must have its own dedicated switch box; it is strictly prohibited to use the same switch box to control 2 or more electrical devices (including sockets). 8.1.4 The power distribution box and the lighting distribution box should be installed separately. When the merging is set to the same distribution box, power and lighting should be supplied via separate circuits ； The power switch box and the lighting switch box must be located separately. 8.1.5 Distribution boxes and switch boxes shall be installed in dry, well-ventilated areas at normal temperatures; they must not be placed in environments with harmful gases, smoke, moisture, or other hazardous substances that could cause damage to them. Nor should they be located in areas prone to impact from external solid objects, severe vibrations, liquid splashes, or exposure to heat sources. Otherwise, it should be removed or protected. 8.1.6 There should be sufficient space and passages around the distribution box and switch box for two people to work simultaneously; no items that may hinder operation or maintenance shall be stored there, nor shall there be any bushes or weeds. 8.1.7 Distribution boxes and switch boxes shall be made of cold-rolled steel plates or flame-retardant insulating materials. The thickness of the steel plates should be between 1.2 and 2.0 mm; the thickness of the steel plates used for switch boxes must not be less than 1.2 mm, while that of the plates used for distribution boxes must not be less than 1.5 mm. The surface of these boxes shall be treated to prevent corrosion. 8.1.8 Distribution boxes and switch boxes shall be installed properly and firmly. The vertical distance from the center of fixed distribution boxes and switch boxes to the ground should be 1.4 to 1.6 meters. Mobile distribution boxes and switch boxes should be installed on sturdy and stable supports. The vertical distance from its center point to the ground should be 0.8–1.6 m. 8.1.9 Electrical appliances (including sockets) inside distribution boxes and switch boxes should first be installed on metal or non-wooden flame-retardant insulating mounting plates, before being securely fastened as a whole inside the distribution box or switch box. The metal electrical mounting plate and the metal enclosure should be electrically connected. 8.1.10 The electrical appliances (including sockets) in the distribution boxes and switch boxes shall be fixed to the electrical installation panels at their designated positions, and must not be tilted or loose. 8.1.11 The electrical installation panel of the distribution box must be equipped with separate terminals for the N wire and the PE wire. The N-terminal block must be insulated from the metal electrical mounting plate ； The PE wire terminal block must be electrically connected to the metal electrical mounting plate. The N wire in the incoming and outgoing lines must be connected through the N wire terminal block ； The PE wire must be connected through the PE wire terminal block. 8.1.12 The connection wires inside distribution boxes and switch boxes must be insulated copper wires. The color markings for wire insulation shall be arranged in an orderly manner in accordance with the requirements of Clause 5.1.11 of these specifications ； Wire branch connections shall not be made by bolt compression; instead, welding should be used along with insulating wrapping, ensuring that no exposed live parts are present. 8.1.13 The metal enclosures of distribution boxes and switch boxes, the metal electrical installation panels, as well as the metal bases and housings of electrical devices when they are not under voltage must be electrically connected to the PE wire through PE wire terminal plates. The metal doors of these boxes must be electrically connected to the metal enclosures using braided soft copper wire. 8.1.14 The dimensions of the distribution boxes and switch boxes should be appropriate to the number and size of the electrical appliances contained within them. The installation dimensions for the electrical appliances on the installation panels inside these boxes can be determined according to Table 8.1.14. 8.1.15 The inlet and outlet ports for wires in distribution boxes and switch boxes shall be located on the bottom surface of the box. Table 8.1.14 Selected values for electrical appliance installation dimensions in distribution boxes and switch boxes. 8.1.16 Fixed wire clamps shall be installed at the inlet and outlet ports of distribution boxes and switch boxes; the wires entering and leaving these boxes shall be fitted with insulating sleeves and bundled together before being secured to the box, so as to avoid direct contact with the box itself. The incoming and outgoing wires of mobile distribution boxes and switch boxes shall use rubber-sheathed insulated cables, with no joints allowed. 8.1.17 The exterior structure of distribution boxes and switch boxes shall be capable of protecting against rain and dust. 8.2 Selection of electrical equipment 8.2.1 The electrical devices in distribution boxes and switch boxes must be reliable and in good condition; it is strictly prohibited to use damaged or substandard electrical equipment. 8.2.2 The electrical equipment in the main distribution panel shall have power isolation capabilities, as well as functions for normally connecting and disconnecting circuits, and for protecting against short circuits, overloads, and electric leakage. The electrical installations should comply with the following principles: 1 When a main leakage protector is installed on the main circuit, a main isolating switch and branch isolating switches, as well as main circuit breakers or branch circuit breakers, and main fuses or branch fuses, should also be installed. When the main leakage protector installed is a circuit breaker that provides protection against short circuits, overloads, and leakage, it may not be necessary to have a main circuit breaker or main fuse. 2 When branch circuit leakage protectors are installed for each branch circuit, a main isolating switch and branch circuit isolating switches, as well as a main circuit breaker and branch circuit breakers, or main fuses and branch circuit fuses, should also be installed. When the leakage protector installed at the branch circuit is a leakage circuit breaker that also has functions for short-circuit, overload, and leakage protection, it may be unnecessary to install a branch circuit breaker or a branch circuit fuse. 3 The isolation switch should be installed at the power supply inlet, and it should be an isolation device that provides a visible disconnection point when switched off, and is capable of disconnecting all poles of the power supply simultaneously. If circuit breakers with visible breaking points are used, there is no need to install a separate isolating switch. 4 Fuses should be products with reliable arc extinguishing and breaking capabilities. 5 The ratings and operating settings of the main switchgear should be compatible with those of the branch switchgear. 8.2.3 The main distribution panel shall be equipped with voltage meters, main current meters, wattmeters, and other necessary instruments. The installation of dedicated electric energy metering instruments shall comply with the requirements of the local power supply and consumption management authorities. When installing a current transformer, its secondary circuit must have a connection point with the protective neutral wire, and it is strictly prohibited to disconnect the circuit. 8.2.4 The distribution box shall be equipped with a main isolating switch and branch isolating switches, as well as a main circuit breaker and branch circuit breakers, or a main fuse and branch fuses. Its setting and selection shall meet the requirements of Article 8.2.2 of these specifications. 8.2.5 The switch box must be equipped with a disconnector, circuit breaker or fuse, as well as a leakage protector. When the leakage protector is a leakage circuit breaker that also has functions for short-circuit and overload protection, it is not necessary to install a circuit breaker or fuse. The isolating switch should be an isolating device that provides a visible disconnection point when switched off, capable of disconnecting all poles of the power supply, and it should be installed at the power inlet side. When the circuit breaker has a visible breaking point, it is not necessary to provide a separate isolating switch. 8.2.6 The isolating switch in the switch box can only be used to directly control lighting circuits and power circuits with a capacity of no more than 3.0 kW, but it should not be operated frequently. Power circuits with a capacity greater than 3.0 kW should be controlled by circuit breakers; when operated frequently, contactors or other starting control devices should also be installed. 8.2.7 The rated values and operating setting values of various switching devices in the switchgear box shall be compatible with the rated values and characteristics of the electrical equipment they control. The specifications of the electrical equipment in the general motor switch box can be selected according to Appendix C of this specification. 8.2.8 The leakage protector shall be installed on the side of the main distribution box or switch box that is closest to the load, and shall not be used to start electrical equipment. 8.2.9 The selection of residual current devices shall comply with the provisions of the current **standards: ‘General Requirements for Residual Current Devices’ GB 6829 and ‘Requirements for the Installation and Operation of Residual Current Devices’ GB 13955. 8.2.10 The rated leakage operating current of the leakage protector in the switch box shall not be greater than 30mA, and the rated leakage operating time shall not be greater than 0.1s. Leakage protectors used in humid or corrosive environments should be splash-proof types, with a rated leakage operating current not exceeding 15mA and a rated leakage operating time not exceeding 0.1s. 8.2.11 The rated leakage operating current of the leakage protector in the main distribution panel shall be greater than 30 mA, and the rated leakage operating time shall be greater than 0.1 s; however, the product of its rated leakage operating current and rated leakage operating time shall not be greater than 30 mA•s. 8.2.12 The number of poles and wires of the leakage protectors in the main distribution box and switch boxes must match the number of phases and wires of the loads on their load side. 8.2.13 For leakage protectors in distribution boxes and switch boxes, it is advisable to use products without an auxiliary power supply (electromagnetic type), or products with an auxiliary power supply that can automatically disconnect in the event of a failure of that supply (electronic type). When using auxiliary power supply-type (electronic) products that cannot be automatically disconnected in the event of a failure of the auxiliary power supply, phase loss protection should also be installed. 8.2.14 The residual current device shall be installed and used in accordance with the product instructions. For residual current devices that have been out of use for a long time and are now being reused or used continuously, their characteristics should be checked on a monthly basis; any issues found should be repaired or the devices replaced promptly. The correct wiring method for using a residual current device should be selected according to Figure 8.2.14. 8.2.15 Plugs and sockets shall not be used for movable connections at the power inlet ends of distribution boxes and switch boxes. Figure 8.2.14 Schematic of the wiring method for using a leakage protector L1, L2, L3 – phase wires ； N – Working neutral wire ； PE – Keep the neutral wire and protective wire ； 1 – Working ground ； 2 – Repeated grounding ； T – Transformer ； RCD – Leakage protector ； H – Lighter ； W – Welding machine ； M – Motor 8.3 Use and Maintenance 8.3.1 The distribution boxes and switch boxes should have names, purposes, circuit identification markings, and system wiring diagrams. 8.3.2 The doors of distribution boxes and switch boxes shall be locked and kept under the responsibility of a designated person. 8.3.3 Distribution boxes and switch boxes should be inspected and maintained regularly. Inspection and maintenance personnel must be professional electricians. During inspection and maintenance, insulating shoes and gloves must be worn as required, electrical insulating tools must be used, and records of the inspection and maintenance work must be kept. 8.3.4 When performing regular maintenance and inspections on distribution boxes and switch boxes, it is necessary to disconnect the corresponding power isolation switch at the upstream level to cut off the power, and hang a sign reading “Do not close – work in progress” to indicate that the power is off; working on these devices while they are still powered is strictly prohibited. 8.3.5 The distribution boxes and switch boxes must be operated in the following sequence: 1. The sequence for supplying power is: main distribution box → sub-distribution box → switch box ； 2 The sequence for power outage operations is: switch box → distribution box → main power distribution box. However, emergency situations involving electrical failures are an exception. 8.3.6 When work at the construction site is suspended for more than 1 hour, the power switch box should be powered off and locked. 8.3.7 The operators of the switchgear box must meet the requirements specified in Article 3.2.3 of these specifications. 8.3.8 No miscellaneous items shall be placed inside the distribution boxes or switch boxes, and they must be kept clean. 8.3.9 No other electrical equipment shall be arbitrarily connected inside the distribution box or switch box. 8.3.10 The electrical equipment and wiring inside distribution boxes and switch boxes must not be altered arbitrarily. When replacing the fuse element, it is strictly prohibited to use an element that does not meet the original specifications. Before use each day, the leakage protector should be tested by pressing the leakage test button once; it must not be used if the test does not proceed normally. 8.3.11 The incoming and outgoing wires of distribution boxes and switch boxes must not be subjected to external forces, and must not come into contact with sharp metal edges, highly corrosive substances, or flammable and explosive materials. 9 Electric construction machinery and hand-held electric tools 9.1 General provisions 9.1.1 The selection, use, inspection, and maintenance of electric construction machinery and hand-held electric tools at construction sites shall comply with the following provisions: 1 The selected electric construction machinery, hand-held electric tools, and their electrical safety devices must meet the requirements of the relevant **current mandatory standards, and they must come with a product certificate and user manual ； 2 Establish and implement a system assigning dedicated personnel and aircraft, along with regular inspections and maintenance ； 3 The grounding shall meet the requirements of Articles 5.1.1 and 5.1.2 of these specifications; there shall be no less than 2 connection points between the metal base and housing of equipment that generates vibration during operation and the PE wire ； 4 The leakage protection meets the requirements of Articles 8.2.5, 8.2.8–8.2.10, as well as Articles 8.2.12 and 8.2.13 of these specifications ； 5 Use, inspect, and maintain in accordance with the instruction manual. 9.1.2 Tower cranes, external elevators, metal operating platforms for slipform templates, and material hoists that require lightning protection devices shall be provided with repeated grounding in addition to being connected to the PE wire. Electrical connection must be ensured between the metal structural components of the equipment. 9.1.3 Plastic enclosures in hand-held electric tools: Class II tools and Class III tools used in hand-held electric tools in general areas do not require a PE wire. 9.1.4 For the supply cables of electric construction machinery and hand-held electric tools, jointless rubber-sheathed copper-core flexible cables should be used based on their calculated load; such cables must meet the requirements specified in Part 1 (General Requirements) and Part 4 (Flexible Wires and Cables) of the current standard **“Rubber-Insulated Cables with a Rated Voltage of 450/750V and Below” GB 5013 ； Its cross-section can be selected according to Appendix C of this specification. The number of core wires in the cable should be determined based on the load, as well as the number of phases and wires in the control equipment; for a three-phase four-wire system, a five-core cable should be used ； For three-phase three-wire systems, a four-core cable should be used ； When single-phase electrical appliances are used in three-phase electrical equipment, a five-core cable should be selected ； For single-phase two-wire systems, a three-core cable should be used. The cable conductors shall comply with the provisions of Clause 7.2.1 of this specification, wherein the PE conductor shall be a green/yellow dual-color insulated wire. 9.1.5 In the switch box of each electric construction machine or hand-held electric tool, in addition to overload, short-circuit, and leakage protection devices, an isolating switch or a circuit breaker with a visible breaking point shall be installed as required by Clause 8.2.5 of this code, and control devices shall be installed as required by Clause 8.2.6 of this code. The control electrical devices in the forward and reverse operation control apparatus shall be automatic control devices such as contactors and relays; manual two-way changeover switches shall not be used as control electrical devices. Electrical specifications can be selected according to Appendix C of this specification. 9.2 Lifting Machinery 9.2.1 The electrical equipment of tower cranes shall meet the requirements specified in the current **standard, the ‘Safety Regulations for Tower Cranes’ GB 5144. 9.2.2 Tower cranes shall be provided with repeated grounding and lightning protection grounding in accordance with the requirements of Article 5.4.7 of these specifications. The installation of the grounding devices for track-mounted tower cranes shall meet the following requirements: 1. A set of grounding devices shall be installed at each end of the track ； Make an electrical connection at the joint of the two tracks, and provide a circular electrical connection at the ends of both tracks ； 3 A set of grounding devices shall be installed every 30 m or less along the longer track. 9.2.3 The safety distance between tower cranes and external power lines shall meet the requirements of Article 4.1.4 of these specifications. 9.2.4 The cables of track-mounted tower cranes must not be dragged along the ground. 9.2.5 Tower cranes that require night operation shall be equipped with floodlights facing the working area. 9.2.6 For tower cranes with a tower height of more than 30 m, red signal lights shall be installed at the top of the tower and at the end of the boom. 9.2.7 Tower cranes operating near strong electromagnetic wave sources require operators to wear insulated gloves and shoes. Insulating isolation measures should be taken between the hook and the crane body, or a temporary grounding device should be attached to the hook when lifting objects from the ground. 9.2.8 Emergency stop switches shall be installed both inside and outside the elevator car for outdoor use. 9.2.9 Limit switches shall be installed at the upper and lower limit positions of outdoor elevators and material hoists. 9.2.10 Before starting operation each day, external elevators and material lifters must undergo a no-load inspection of their travel switches, limit switches, emergency stop switches, drive mechanisms, and brakes; they may be used only after everything is functioning properly. Fall prevention measures must be in place during inspection. 9.3 Pile-driving machinery 9.3.1 The sealing performance of the motors for submersible drilling machines shall meet the requirements of IP68 as specified in the current standard \"Degrees of protection provided by enclosures (IP codes)\", GB 4208. 9.3.2 The load cable for the submersible motor shall be a flexible copper-core cable with a waterproof rubber sheath, with a length of not less than 1.5 m, and it must not be subjected to external forces. 9.3.3 The residual current device in the switch box of the submersible drilling machine must meet the requirements for residual current devices used in humid environments as specified in Article 8.2.10 of these specifications. 9.4 Earthmoving Machinery 9.4.1 The residual current devices in the switchboxes of earthmoving machinery must meet the requirements specified in Article 8.2.10 of these specifications regarding residual current devices to be used in humid environments. 9.4.2 The connection points for the PE wire of the compaction machinery shall be no less than 2. 9.4.3 The load line of the ramming machine shall use a weather-resistant rubber-sheathed copper-core flexible cable. 9.4.4 When using ramming machinery, insulating equipment must be worn as required, and a dedicated person should be assigned to adjust the cables during use; the length of the cables should not exceed 50 m. Cables must not be twisted, kinked, or crossed by earthmoving machinery. 9.4.5 When multiple ramming machines operate side by side, the distance between them shall not be less than 5 m ； When working in sequence, the distance between them must be no less than 10m. 9.4.6 The control handles of compaction machinery must be insulated. 9.5 Welding Machinery 9.5.1 Welding machinery should be placed in a location that is protected from rain, dry, and well-ventilated. Flammable and explosive materials are not allowed at the welding site. 9.5.2 The length of the primary side power cable of the AC arc welding machine transformer should not exceed 5 m, and a protective cover must be installed at the power inlet. The commutator of a generator-type DC welding machine should be regularly inspected and maintained to eliminate any abnormal electric sparks that may occur. 9.5.3 The leakage protectors in the switch box of welding machinery must meet the requirements of Article 8.2.10 of these specifications. AC welding machines should be equipped with secondary-side electric shock protection devices. 9.5.4 The secondary cable of welding machinery shall be a flexible copper-core cable with a waterproof rubber sheath; the length of the cable shall not exceed 30 m. Metal components or structural rebar shall not be used as a substitute for the ground wire of the secondary cable. 9.5.5 Protective equipment must be worn when using welding machinery for welding. Welding work in the open rain is strictly prohibited. 9.6 Handheld electric tools 9.6.1 In areas where the air humidity is below 75%, Class I or Class II handheld electric tools can be used; there must be no less than 2 connection points between the metal casing and the PE wire ； Except for plastic-encased Class II tools, the rated leakage operating current of the residual current device in the relevant switch box should not exceed 15 mA, and the rated leakage operating time should not exceed 0.1 s; the plug of its load cable should be equipped with dedicated protective contacts. The sockets and plugs used should be structurally consistent to prevent the mixing of conductive contacts and protective contacts. 9.6.2 When operating in humid areas and on metal frameworks, Class II or Class III hand-held power tools powered by a safety isolation transformer must be used. When using metal-clad Class II hand-held power tools, they must meet the requirements of Clause 9.6.1 of these specifications ； Their switch boxes and control boxes should be located outside the work area; the use of Class I handheld electric tools is strictly prohibited in humid areas or on metal frameworks. 9.6.3 In confined spaces, Class III handheld electric tools powered by safety isolation transformers must be used; both their switch boxes and the safety isolation transformers should be located outside the confined space, and a PE wire must be connected. The selection of residual current devices shall comply with the requirements for such devices in humid or corrosive environments as specified in Article 8.2.10 of these specifications. Someone should be monitoring from outside during the operation. 9.6.4 The load cable for hand-held power tools shall be a weather-resistant rubber-sheathed copper-core flexible cable, and must not have any joints. 9.6.5 The casing, handle, plug, switch, load cable, etc. of handheld power tools must be in good condition. Insulation checks and no-load tests must be carried out before use; the tools can only be used once the insulation meets the requirements and they operate properly under no-load conditions. The insulation resistance shall not be less than the value specified in Table 9.6.5. Table 9.6.5 Insulation resistance limits for hand-held power tools Note: Insulation resistance is measured using a 500V megohmmeter. 9.6.6 When using hand-held power tools, insulating protective equipment must be worn as required. 9.7 Other electric construction machinery 9.7.1 The leakage protection for equipment such as concrete mixers, insert vibrators, plate vibrators, floor finishers, terrazzo machines, steel bar processing machinery, woodworking machinery, shield machines, and water pumps shall meet the requirements of Article 8.2.10 of these specifications. 9.7.2 The power cables for concrete mixers, insertion vibrators, plate vibrators, floor finishers, terrazzo machines, steel bar processing machinery, woodworking machinery, and shield tunneling machinery must be weather-resistant flexible cables with copper cores, and must be free of any damage or joints. The load cable for the water pump must be a flexible copper-core cable with a waterproof rubber sheath; it must not have any damage or connections, and it must not be subjected to any external forces. The load line of the shield machine must be firmly fixed, with a height from the ground of not less than 2.5 m. 9.7.3 When cleaning, inspecting, or repairing equipment such as concrete mixers, steel bar processing machinery, woodworking machinery, and shield tunneling machines, it is necessary to first disconnect the power supply at their switch boxes, ensure that there is a visible point where the power is cut off, and then close and lock the doors. 10 Lighting 10.1 General Provisions 10.1.1 In pits, holes, wells, during night work, or in areas such as factories, roads, warehouses, offices, canteens, dormitories, material storage areas, and places with poor natural lighting, general lighting, local lighting, or a combination of both should be provided. In a workplace, local lighting alone shall not be provided. At construction sites where operators need to evacuate promptly in the event of a power outage, emergency lighting equipped with a backup power source must be installed. 10.1.2 Field lighting should use lighting sources with high luminous efficiency and long lifespan. For areas that require extensive lighting, high-pressure mercury lamps, high-pressure sodium lamps, or halogen-tungsten lamps for mixed lighting should be used. 10.1.3 The selection of lighting fixtures must be determined based on the following environmental conditions: 1 In areas with normal humidity, open-type lighting fixtures should be used ； 2 In humid or highly humid areas, use sealed waterproof lighting fixtures or open-type lighting fixtures equipped with waterproof lamp holders ； 3 In areas with a high amount of dust but no risk of explosion or fire, use dust-proof lighting fixtures ； 4 In areas with explosion and fire hazards, explosion-proof lighting fixtures should be used according to the hazard level of the area ； 5 In areas with strong vibrations, use vibration-resistant lighting fixtures ； 6 In areas with strongly corrosive substances such as acids and alkalis, use acid- and alkali-resistant lighting fixtures. 10.1.4 The quality of lighting fixtures and equipment shall comply with the provisions of **current relevant mandatory standards; fixtures and equipment with aged or damaged insulation shall not be used. 10.1.5 For underground large-scale construction sites without self-illumination, a separate lighting power consumption plan shall be prepared. 10.2 Lighting Power Supply 10.2.1 For general areas, lighting fixtures with a rated voltage of 220V are suitable. 10.2.2 Safety extra-low voltage lighting fixtures should be used in the following special locations: Lighting in tunnels, civil air defense facilities, areas with high temperatures, areas with conductive dust, relatively humid environments, or places where the height of the lighting fixtures above the ground is less than 2.5 meters; the supply voltage in such cases should not exceed 36V ； 2 For lighting in humid areas and locations where live electrical parts are easily accessible, the supply voltage must not exceed 24V ； 3 For lighting in particularly humid areas, on conductive floors, inside boilers, or metal containers, the supply voltage must not exceed 12V. 10.2.3 The use of row lights shall meet the following requirements: 1 The supply voltage shall not exceed 36V ； 2 The lamp body and handle should be sturdy, well-insulated, and resistant to heat and moisture ； 3 The lamp base is firmly attached to the lamp body, and the lamp base has no switch ； 4 The bulbs have a metal protective mesh on the outside ； 5 The metal mesh, reflector, and suspension hooks are fixed to the insulated parts of the lamp. 10.2.4 For small work areas far from power sources, road lighting, security lighting, or lighting systems with a rated voltage of 12–36V, the allowable voltage deviation is -10% to 5% of the rated voltage value ； For the remaining locations, the allowable voltage deviation is ±5% of the rated voltage value. 10.2.5 Lighting transformers must be double-winding safety isolation transformers; autotransformers are strictly prohibited. 10.2.6 The lighting system should ensure a balanced three-phase load; on each single-phase circuit, the number of lights and sockets should not exceed 25, and the load current should not exceed 15A. 10.2.7 The primary side power cable of the portable transformer shall be a flexible copper cable with rubber or plastic insulation, without any joints in between; its length should not exceed 3 m. The green/yellow dual-colored wire may only be used as a PE wire, and the power plug shall be equipped with protective contacts. 10.2.7 The cross-sectional area of the working neutral wire shall be selected in accordance with the following provisions: 1 In single-phase two-wire and two-phase two-wire circuits, the cross-sectional area of the neutral wire is the same as that of the phase wires ； 2 In three-phase four-wire systems, when the lighting fixtures are incandescent lamps, the cross-sectional area of the neutral wire shall be not less than 50% of that of the phase wires ； When the light source is a gas discharge lamp, the cross-sectional area of the neutral wire is selected based on the current of the phase with the maximum load ； 3 In a three-phase lighting circuit with phase-by-phase disconnection, the cross-sectional area of the neutral wire is the same as that of the phase wire carrying the maximum load. 10.2.9 The installation of indoor and outdoor lighting circuits shall comply with the requirements of Chapter 7 of these specifications. 10.3 Lighting fixtures 10.3.1 The metal enclosures of lighting fixtures must be connected to the PE wire. The lighting switch box must be equipped with a disconnect switch, devices for protecting against short circuits and overloads, as well as a leakage protector; these requirements shall comply with Articles 8.2.5 and 8.2.6 of these specifications. 10.3.2 Outdoor 220V lighting fixtures must be installed at a height of no less than 3m above the ground, while indoor 220V lighting fixtures must be installed at a height of no less than 2.5m above the ground. The distance between ordinary lighting fixtures and flammable materials should not be less than 300 mm ； High-heat lighting devices such as spotlights and iodine-tungsten lamps should be kept at a distance of no less than 500 mm from flammable materials, and must not shine directly on them. When the required safety distance cannot be maintained, thermal insulation measures should be taken. 10.3.3 Each lamp post light should be equipped with a fuse for protection separately. The lamp holder cable should have waterproof bends. 10.3.4 Fluorescent tubes should be fixed using tube holders or suspended with suspension chains; the ballasts for fluorescent lamps must not be installed on flammable structures. 10.3.5 The installation height of iodine-tungsten lamps and metal halide lamps such as those using sodium, thallium, indium, etc., should be above 3 m. The lamp wires must be fixed to the terminals and must not be close to the surface of the lamp. 10.3.6 The base of the spotlight should be installed firmly, and the pivot should be tightened and fixed in the desired axis direction. 10.3.7 Screw-type lamp holders and their wiring shall meet the following requirements: 1. The insulated housing of the lamp holder must be free from damage and leakage ； The 2-phase wires are connected to the end attached to the center contact, while the neutral wire is connected to the end attached to the threaded port. 10.3.8 The wiring inside the lamp must be secure, while the wiring outside the lamp must be properly insulated and protected from moisture. 10.3.9 The lighting fixtures for temporary structures should be controlled by pull-cord switches, and the installation location of these switches should meet the following requirements: 1 The pull-cord switch should be located at a height of 2–3 meters above the ground, and at a horizontal distance of 0.15–0.2 meters from the entrance/exit; the end of the pull cord should point downward ； 2 The height of the other switches from the ground is 1.3 m, and their horizontal distance from the entrance/exit is 0.15～0.2 m. 10.3.10 The phase wire of the lamp must be controlled by a switch; the phase wire shall not be connected directly to the lamp. 10.3.11 For construction projects and mechanical equipment that affect the movement of aircraft or vehicles at night, conspicuous red signal lights must be installed. Their power supply should be located in front of the main power switch at the construction site, and an emergency backup power source should be provided in case the external power supply is disconnected. Appendix A: Average annual number of thunderstorm days nationwide Table A: Average annual number of thunderstorm days in major cities across the country Continued from Table A Continued from Table A Continued from Table A Continued from Table A Note: a denotes year, and d denotes day. Appendix B: Ball Rolling Method B.0.1 According to the ball rolling method, the protection area of a single lightning rod (based on the spark arrester) shall be determined as follows: 1 When the height of the lightning rod (h) is less than or equal to the ball rolling radius (hr) (Figure B.0.1-1), the protection radius of the lightning rod at the XX′ level corresponding to the height of the protected object, as well as its protection radius at ground level, can be calculated using the following formulas: Figure B.0.1-1 Protection area of a single lightning rod (h≤hr) Where h is the height of the lightning rod in meters ； hx——height of the protected object (m) ； rx —— protection radius at the XX′ plane at the height of the protected object (m) ； ro——Protection radius on the ground (m) ； hr——ball rolling radius (m). In the current **standard, the Code for Design of Lightning Protection of Buildings GB 50057, the rolling sphere radii for buildings classified as Category 1, 2, and 3 in terms of lightning protection are specified as 30m, 45m, and 60m respectively. For general construction sites in areas where the average annual number of thunderstorm days is greater than 15 days per year, tall structures and buildings with a height of 15 meters or more, as well as large construction machinery ； Or in areas where the average annual number of thunderstorm days is 15 days per year or less, tall structures and large construction machinery at a height of 20 meters or more can be treated in accordance with Category III lightning protection buildings. 2 When the height of the lightning rod (h) is greater than the rolling sphere radius (hr) (Figure B.0.1-2), the protection radius of the lightning rod at the XX′ level corresponding to the height of the structure being protected, as well as its protection radius at ground level, can be determined using the following formulas: B.0.2 According to the rolling sphere method, the protection area of a single lightning conductor (paratonnerre) should be determined in the following manner: When the height of the lightning conductor is greater than or equal to 2 times the rolling sphere radius, there is no protection area ； When the height of the lightning protection conductor is less than 2 times the rolling sphere radius (Figure B.0.2), the space between the arc formed by 2 times the rolling sphere radius (the cylindrical surface) and the ground constitutes the protection area. When hr＜h＜2hr, the height ho of the highest point within the protection area can be calculated using the following formula: When h≤hr, the height of the highest point within the protection area is equal to h: ho=h (B.0.2-2). The protection width bx of the lightning conductor at a height of hx in the XX′ plane can be calculated using the following formula: Figure B.0.1-2 shows the protection area covered by a single lightning rod (h＞hr), while Figure B.0.2 shows the protection area covered by a single overhead lightning conductor. The protection areas at both ends of the lightning conductor are determined using the method applicable to a single lightning rod. The protection areas covered by multiple lightning rods and multiple lightning conductors shall be determined in accordance with the current **standard, the Code for Design of Lightning Protection of Buildings GB 50057. Appendix C Motor Load Lines and Electrical Appliance Selection Table C Motor Load Lines and Electrical Appliance Selection Continued Table C Continued Table C Glossary of Terms Used in This Specification 1. To facilitate differentiated treatment when implementing the provisions of this specification, the terms with varying levels of strictness are defined as follows: 1) Indicates a very high level of strictness – it is mandatory to follow this requirement: The positive term used is “must”” ； The antonym uses “strictly prohibited”” ； 2) Indicates strictness – it should be done under normal circumstances: the positive term uses “should”” ； The negative form uses “should not” or “must not”” ； 3) Indicates that a slight choice is allowed, and that this should be done first when conditions permit: the positive term used is “it is appropriate”” ； The antonym uses “not suitable”” ； To indicate that there is a choice and that it is possible to do so under certain conditions, use “can”. Where the two provisions specify that execution should be in accordance with other relevant standards, it shall be expressed as “should be executed in accordance with...” or “should comply with...provisions (requirements)”. Technical Code for Safety of Temporary Electricity Use at Construction Sites JGJ46-2005 Explanations of the Provisions Preface The Technical Code for Safety of Temporary Electricity Use at Construction Sites, JGJ46-2005, was approved and issued by the Ministry of Construction via Announcement No. 322 on April 15, 2005. The leading institution for the first edition of this standard was Shenyang Institute of Building Engineering, with the China Academy of Building Research participating as well. To enable relevant personnel from design, construction, research, educational institutions, and other organizations to correctly understand and implement the provisions of these standards when using them, the drafting team of the \"Technical Code for Safety in Temporary Electricity Use at Construction Sites\" has prepared explanatory notes for each chapter, section, and article of these standards for reference by users in China. If you find any inaccuracies in the explanations provided for this provision during use, please send your comments to Shenyang Jianzhu University. Table of Contents 1 General Provisions 3 Temporary Power Supply Management 3.1 Organizational Design for Temporary Power Supply 3.2 Electricians and Personnel Using Electricity 3.3 Safety and Technical Documentation 4 Protection of External Power Lines and Electrical Equipment 4.1 Protection of External Power Lines 4.2 Protection of Electrical Equipment 5 Grounding and Lightning Protection 5.1 General Provisions 5.2 Protective Zero Connection 5.3 Grounding and Ground Resistance 5.4 Lightning Protection 6 Distribution Rooms and Self-Provided Power Sources 6.1 Distribution Rooms 6.2 230/400V Self-Provided Generator Sets 7 Distribution Lines 7.1 Overhead Lines 7.2 Cable Lines 7.3 Indoor Wiring 8 Distribution Boxes and Switch Boxes 8.1 Installation of Distribution Boxes and Switch Boxes 8.2 Selection of Electrical Devices 8.3 Use and Maintenance 9 Electric Construction Machinery and Handheld Electric Tools 9.1 General Provisions 9.2 Lifting Machinery 9.3 Piling Machinery 9.4 Earthmoving Machinery 9.5 Welding Machinery 9.6 Handheld Electric Tools 9.7 Other Electric Construction Machinery 10 Lighting 10.1 General Provisions 10.2 Lighting Power Supply 10.3 Lighting Devices 1 General Provisions 1.0.3 This clause comprehensively stipulates the three basic safety and technical principles that must be fully implemented in the electrical systems within the scope of application of these specifications. They serve as the main technical basis for ensuring safety in electrical installations at construction sites ； It is also a key technical measure to ensure electrical safety and prevent electric shock and electrical fire accidents. 3 Management of Temporary Electricity Use 3.1 Organizational Design for Temporary Electricity Use 3.1.1 The likelihood of electric shock and electrical fire accidents is related to the number, type, distribution of electrical equipment, as well as the calculated load. For construction sites where there is a large amount of electrical equipment (5 units or more) and the total capacity of such equipment is high (50 kW or more), in order to standardize the management of temporary electricity use, enhance electrical safety measures, and ensure safe electricity usage, this section provides guidelines for the organizational design of electrical systems based on the actual conditions at the construction site, in accordance with the current industry standard \"Safety Regulations for Electric Power Construction (Substation Section)\” DL 5009.3. These guidelines serve to guide the construction of electrical systems and ensure their safe and reliable operation. 3.1.2 This clause specifies the contents of the temporary power supply organization design, including the tasks that need to be completed, and is applicable universally. The basis for load calculation includes the capacity, type, grouping, and operating patterns of electrical equipment; the demand factor method can be employed ； Drawing the layout plan of the power distribution equipment is merely a requirement for installing distribution cabinets in rows within the power distribution room ； Both electrical safety measures and electrical fire prevention measures include technical and managerial aspects. 3.1.3 The temporary power supply organization design is a separate technical document. To ensure its role in guiding the safety of temporary power supply systems and electrical usage at the construction site, the relevant drawings must be prepared separately and shall not be combined with those from other types of construction organization designs. 3.1.4 and 3.1.5: To strengthen management and clarify responsibilities, these two clauses, in accordance with the current **standard \"Guidelines for Electrical Safety\" GB/T 13869 and the current industry standard \"Safety Procedures for Electric Power Construction (Substation Section)\" LD 5009.3, and taking into account the actual electrical usage conditions at construction sites, specify the procedures for preparing electrical organization designs and any changes to them, as well as the processes for reviewing and approving such designs. Among them, the relevant departments responsible for reviewing the temporary power supply organization design are the departments related to safety, technology, equipment, construction, materials, and supervision. 3.1.6 For smaller construction sites that meet the specified requirements, it may not be necessary to prepare an electrical utilization plan; however, safety measures for electrical use and electrical fire prevention measures must still be established. Just like in the case of temporary electrical utilization plans, the same procedures for preparation, review, and approval must be strictly followed. 3.2 Electricians and Persons Using Electricity 3.2.1 This clause is based on the provisions of the current **standard, the ‘Guidelines for Electrical Safety’ GB/T 13869, which prohibit persons who are not electricians from performing electrical work. 3.2.2 In accordance with the provisions of the current **standard ‘Guidelines for Electrical Safety’ GB/T 13869, and taking into account the characteristics of work at construction sites, this section sets out clear requirements regarding the electrical operation skills and protective skills of various personnel involved in electrical work, as well as matters related to education, training, and technical instructions. The persons using electricity as referred to in this article are those who directly operate electrical equipment for construction work. 3.2.3 This clause specifies that electricians and users of electrical equipment must work with valid certificates after receiving training. Electrical equipment refers to any facility or product used for power generation, transformation, transmission, distribution, or consumption, such as motors, transformers, electrical appliances, electrical measuring instruments, protective devices, wiring systems, and electrical tools. It also encompasses the mechanical assemblies or structural components associated with these devices, such as various electric machinery, power tools, lighting fixtures, welding machines, etc. Among them, electrical equipment that converts electrical energy into other forms of energy, such as motors, welders, lighting fixtures, electric machinery, and power tools, are also known as electrical load devices. 3.3 Safety Technology Documents 3.3.1 Among the 8 types of safety technology documents specified in this section, the test and inspection certificates for electrical equipment as well as the commissioning records shall be provided by the equipment manufacturer or by professional maintenance personnel. Articles 3.3.3 and 3.3.4 stipulate the inspection system for temporary electrical installations at construction sites and the procedures for carrying out such inspections. The maximum execution frequency is once a month at the construction site ； At the grassroots company, once per quarter. 4 Protection of Electrical Lines and Equipment 4.1 Protection of External Electrical Lines 4.1.1 This section sets out specific isolation protection measures to prevent direct electric shock to workers at construction sites, in accordance with the current **standard \"General Requirements for Devices and Equipment for Protection against Electric Shock\" GB/T 17054, as well as the International Electrotechnical Commission standard \"General Requirements for Devices and Equipment for Protection against Electric Shock\" IEC 1140:1992 regarding the principles of electrical isolation for protection. 4.1.2 The provisions in this clause are established in accordance with the principles regarding protection against direct contact set out in the current standard **\"Electrical Installations in Buildings – Protection Against Electric Shock\" GB 14821.1, as well as the current standard **\"Design Code for Overhead Power Lines of 66 kV and Below\" GB 50061 and the industry standard **\"Safety Work Procedures\" DL 409. Taking into account factors such as the erection of external scaffolding at construction sites and the activities of construction workers, these provisions specify the minimum safe operating distances necessary to prevent human beings from coming into direct contact with, or being in close proximity to, overhead power lines, either directly or indirectly through metal objects. The requirements set out in this provision are higher than those specified in the current industry standard, the \"Safety Regulations for Electric Power Work (Power Line Section)\». This is done, on the one hand, to ensure the safety of construction operations ； On the other hand, it provides space for installing protective facilities when the specified requirements are not met. 4.1.3 This clause is formulated in accordance with the current **standard \"Code for Design of Overhead Power Lines of 66 kV and Below\" GB 50061, and specifies the minimum safety distances to prevent direct or indirect contact with overhead power lines, taking into account factors such as vehicle transportation of materials at the construction site. 4.1.4 This clause is formulated in accordance with the current **standard \"Safety Regulations for Tower Cranes\" GB 5144 and the current industry standard \"Safety Work Regulations for Power Construction (High-Voltage Power Line Section)\" DL 5009.2. It sets out provisions to prevent cranes (including their booms and lifting ropes) as well as the items being lifted from coming too close to high-voltage power lines, and to prevent the dropped items from damaging such high-voltage power lines, taking into account factors such as the swinging motion of the items being lifted during crane operations. 4.1.6 The protective facilities specified in this clause comply with the current **standard \"Protection against electric shock in electrical installations of buildings\" GB 14821.1, as well as the corresponding International Electrotechnical Commission standard \"Safety requirements for electrical installations of buildings – Protection against electric shock\" IEC 364-4-41 (1992), regarding protective measures such as barriers, enclosures, and obstacles for preventing direct contact. Protective structures should be constructed using wood, bamboo, or other insulating materials, and should not be built from metal materials such as steel pipes. Warning signs on protective facilities must be clearly visible day and night. The minimum safe distance between protective facilities and external power lines is determined in accordance with the provisions set out in the current industry standard \"Safety Regulations for Power Construction (High-Voltage Power Line Section)\", DL 5009.2, regarding the minimum safe distance for work at heights and in proximity to live electrical conductors. Robust and stable protective facilities mean that they are capable of withstanding accidental impacts from falling people, tools, and equipment during construction, while maintaining their protective function. The IP31 rating specifies that the gaps in the protective enclosure prevent solid objects with a diameter of ø2.5mm from passing through. 4.1.7 This clause specifies further measures to be taken when the protection requirements of clause 4.1.6 cannot be met, emphasizing that construction must not proceed without any such measures in place. 4.2 Protection of electrical equipment 4.2.1 This section complies with the provisions of the current standards **“Guidelines for Electrical Safety” GB/T 13869, “Design Code for Electrical Installations in Explosive and Flammable Environments” GB 50058, and “Degrees of Protection Provided by Enclosures (IP Code)” GB 4208, and is suitable for the working conditions at construction sites. Regarding the protection of flammable and explosive materials, the specified protective measures and protection levels refer to the protective structures and measures for electrical equipment that are appropriate to the category of danger and the scope of the area ； For protection against pollution sources and corrosive agents, the specified protective measures and protection levels refer to the protective structures or measures that electrical equipment should have in environments already present with such pollution sources and corrosive agents, in order to be compatible with those environmental conditions. 4.2.2 This clause is formulated in light of the practice of installing electrical equipment outdoors at construction sites and of concurrent operations by different types of workers, aiming to prevent electrical accidents caused by mechanical damage to such equipment. 5 Grounding and Lightning Protection 5.1 General Provisions Articles 5.1.1 and 5.1.2, in accordance with the current standard \"Types of System Grounding and Safety Technical Requirements\" GB 14050 and taking into account the actual conditions at construction sites, specify the basic types of system grounding suitable for temporary electrical systems at such sites. They emphasize the use of the TN-S neutral protection system, prohibit the use of the TN-C system, and clearly define the methods for implementing the TN-S system in order to avoid the potential hazards associated with mixing TN and TT systems. The neutral point refers to the common connection point when a three-phase power supply is connected in a Y configuration. The neutral wire refers to the conductor that leads from the neutral point. The working neutral wire refers to the wire that extends from the neutral point when the neutral point is grounded, and serves as a power line, providing a path for power during operation. The protective neutral wire refers to a wire that is derived from the neutral point or the neutral line when the neutral point is grounded; it is not used as a power supply wire, but solely as a conductor for connecting the exposed conductive parts of electrical equipment. During operation, it serves only as a path for leakage current. 5.1.3 This clause is a supplementary provision to ensure that the TN-S system remains unaltered, and it is in compliance with the current **standard \"Types of System Grounding and Safety Technical Requirements\" GB 14050. 5.1.4 This clause is in compliance with the current **standard \"Types and Safety Technical Requirements for System Grounding\" GB 14050. 5.1.5 This clause is in line with the current **standard \"Technical Requirements for Isolation Transformers and Safety Isolation Transformers\" GB 13028, which is an equivalent adoption of the International Electrotechnical Commission standard \"Requirements for Isolation Transformers and Safety Isolation Transformers\" IEC 742 (1983), as well as the provisions of the current **standard \"Types of System Grounding and Their Safety Technical Requirements\" GB 14050. 5.1.6 This clause complies with the provisions of the current **standard, ‘Guidelines for Electrical Safety’ GB/T 13869. The phase wires are the three power lines that originate from the three separate power terminals of a three-phase power supply (generator or transformer) (denoted as L1, L2, L3 or A, B, C); they are also known as terminal wires and commonly referred to as live wires. 5.1.7 This clause is formulated in accordance with the current industry standard, the \"Code for Electrical Design of Civil Buildings\" JGJ/T 16, and ensures that the grounding resistance meets the required standards throughout the year. In Table 5.1.7, grounding electrodes with a burial depth greater than 2.5 m are referred to as “deeply buried grounding electrodes”. Clauses 5.1.8 and 5.1.9 are in compliance with the current standards **“Types and Safety Technical Requirements for System Grounding” GB14050, “Electrical Installations in Buildings – Part 5: Selection and Installation of Electrical Equipment, Chapter 54: Grounding Devices and Protective Conductors” GB 16895.3 (which is equivalent to the International Electrotechnical Commission standard IEC 364-5-54:1980), as well as the current industry standard **“Code for Electrical Design of Civil Buildings” JGJ/T 16. 5.1.10 This clause is in compliance with the current **standards \"Types and Safety Technical Requirements for System Grounding\" GB 14050, \"Design Code for Substations of 10 kV and Below\" GB 50053, the current **standard \"Color or Numerical Marking of Conductors\" GB 7947 (i.e., IEC standard IEC 446:1989), as well as the current **standard \"Code for Acceptance of Construction Quality of Building Electrical Engineering\" GB 50303. 5.2 Protective Zero Connection 5.2.1 This clause complies with the provisions regarding the zero connection protection of electrical equipment in the current standards **“Types and Safety Technical Requirements for System Grounding” GB 14050 and “Code for Construction and Acceptance of Grounding Systems in Electrical Installation Projects” GB 50169. 5.2.2 This clause is in accordance with the current **standard \"General requirements for protection against electric shock – Apparatus and equipment\" GB 17045 (which is equivalent to the International Electrotechnical Commission standard IEC 446:1992), as well as the current national standard \"Electrical installations in buildings – Protection against electric shock\" GB 14821.1, and the International Electrotechnical Commission standard \"Electrical installations in buildings – Protective measures against electric shock\" IEC 364-4-41:1992, which is adopted equivalently by this standard. 5.2.3 This clause is in compliance with the current **standard \"Code for Construction and Acceptance of Grounding Systems in Electrical Installation Projects\" GB 50169. 5.3 Grounding and Ground Resistance 5.3.1 This section complies with the current industry standard, the \"Code for Electrical Design of Civil Buildings\" JGJ/T 16. 5.3.2 This clause specifies the requirements for the grounding of the protective neutral wire in TN systems, in accordance with the principles set out in the current **standard \"Types and Safety Technical Requirements for System Grounding\" GB 14050. The regulations regarding the repeated grounding of the protective neutral wire in the TN system, as well as the value of the grounding resistance, are designed to reduce the voltage of the protective conductor with respect to ground in the event that the PE wire breaks at some point, and subsequently there is a short circuit or leakage current between the phase conductors of the electrical equipment and the protective conductor (or the exposed conductive parts of the equipment). This ensures that the protective devices installed in the system can cut off the power supply within a specified time frame. These requirements are expressed by the following two equations:
Zs•Ia ≤ U0
Zs•IΔn ≤ U0
Where Zs represents the impedance of the fault circuit (Ω) ； It—is the short-circuit setting current (A) of the short-circuit protection device ； IΔn ——Rated leakage operating current of the residual current device (A) ； U0——Power supply voltage of the faulty circuit (V). 5.3.3 This clause is another supplementary provision to ensure that the TN-S system remains unaltered. 5.3.4 This clause is formulated in accordance with the requirements of the current **standard \"Electrical Installations in Buildings – Part 5: Selection and Installation of Electrical Equipment, Chapter 54: Earthing Arrangements and Protective Conduits\" GB 16895.3 (which is equivalent to the International Electrotechnical Commission standard IEC 364-5-54:1980), as well as the current industry standard \"Code for Electrical Design of Civil Buildings\" JGJ/T 16. Among them, the minimum specified dimensions for materials used as artificial grounding electrodes are as follows: the thickness of angle steel plates must be no less than 4 mm, the wall thickness of steel pipes must be no less than 3.5 mm, and the diameter of round steel must be no less than 4 mm ； The reason why deformed steel bars are not allowed to be used is mainly that they have difficulty making close contact with the soil, resulting in unstable grounding resistance. Points 5.3.5 and 5.3.6 are in line with the current industry standard, the \"Code for Electrical Design of Civil Buildings\" JGJ/T 16, and take into account the fact that generators are primarily used as a power source to maintain supply when external power lines fail. 5.3.7 This clause is in line with the provisions on static electricity protection measures in the current **standard \"General Guidelines for Preventing Static Electricity Accidents\" GB 12158. 5.4 Lightning Protection 5.4.1 This clause is in line with the current industry standard, the \"Code for Electrical Design of Civil Buildings\" JGJ/T 16, which specifies measures to prevent lightning waves from penetrating distribution equipment via overhead lines in cases where no lightning arresters are used. Sections 5.4.2 to 5.4.5 comprehensively specify the installation and requirements for lightning protection devices at construction sites, in accordance with the current standards **\"Code for Design of Lightning Protection of Buildings\" GB 50057 and \"Safety Regulations for Tower Cranes\" GB 5144, taking into account the average annual number of thunderstorm days across different regions as well as the height of mechanical equipment at construction sites. The protection area of the lightning receptor in the lightning protection systems of adjacent buildings, structures, and other facilities refers to the protection area determined by the ball rolling method. The so-called rolling ball method involves selecting a spherical object with a radius hr, determined by the lightning protection category, and rolling it along the area that needs to be protected from direct lightning strikes. If the sphere comes into contact only with the lightning conductor (including metal objects used as lightning conductors), or only with the lightning conductor and the ground (including metal objects in contact with the earth and capable of withstanding lightning strikes), without touching the area that needs protection, then that part is protected by the lightning conductor. The protection area of a single lightning rod (lightning receptor) is shown in Figures B.0.1 and B.0.2; it consists of a symmetric cone formed by the areas between the arc curves MA′ and MB′ and the ground, as well as between the arc curves M′A′ and M′B′ and the ground. The power, control, lighting, signaling, and communication circuits of mechanical equipment are laid using steel pipes, and they are electrically connected to the metal structure of the equipment in order to prevent the hazards caused by lightning strikes through shielding and equipotential bonding. 5.4.6 This clause complies with the general requirements for determining the grounding resistance value for lightning protection impacts as specified in the current **standard, the Code for Design of Lightning Protection of Buildings GB 50057. 5.4.7 This clause complies with the principles specified in the current **standard \"Code for Design of Lightning Protection of Buildings\" GB 50057; the value of the comprehensive grounding resistance meets the requirement set out in the current **standard \"Safety Regulations for Tower Cranes\" GB 5144, which stipulates that the grounding resistance of cranes should not exceed 4Ω. 6 Distribution Rooms and Self-Provided Power Sources 6.1 Distribution Rooms 6.1.1 This section complies with the provisions of the current **standard, the ‘Code for Design of Low-Voltage Distribution Systems’ GB 50054. 6.1.2 This clause is in accordance with the provisions of the current **standard \"Design Code for Substations of 10 kV and Below\" GB 50053. 6.1.3 This clause meets the requirements for the construction of distribution rooms specified in the current **standard, ‘Design Code for Substations of 10 kV and Below’ GB 50053. 6.1.4 This clause is in compliance with the provisions of the current **standards, namely the ‘Design Code for Substations of 10 kV and Below’ GB 50053 and the ‘Design Code for Low-Voltage Distribution Systems’ GB 50054. 6.1.5 This clause is formulated in accordance with the current **standard \"Design Code for Electrical Measuring Instrument Installations in Power Equipment\" GBJ 63. 6.1.6 This clause is formulated in accordance with the current **standard \"Code for Design of Low-Voltage Power Distribution\" GB 50054, taking into account the need to ensure reliable control and protection of power supply circuits at construction sites, as well as the requirement to install leakage protection systems. Articles 6.1.7 to 6.1.9 are technical regulatory provisions designed to ensure the safe and reliable use of electrical systems at construction sites, as well as the safety during power outages for maintenance purposes and during the process of turning power on and off. 6.2 230/400V self-provided generator sets 6.2.1～6.2.3 These three clauses comply with the provisions of the current industry standard, the \"Code for Electrical Design of Civil Buildings\" JGJ/T 16. 6.2.4 The provisions of this article are consistent with Article 5.1.1. 6.2.5 This clause is in accordance with the provisions of the current **standard, ‘Design Code for Electrical Measuring Instrumentation in Power Installations’ GBJ 63. 6.2.6 This clause meets the general requirements of the current industry standard \"Code for Electrical Design of Civil Buildings\" JGJ/T 16, and further emphasizes the need to ensure power isolation as well as protection against short circuits, overloads, and electric leakage in construction electrical systems. 6.2.7 This clause complies with the requirements of the current **standard, the ‘Code for Safety of Power Supply and Consumption at Construction Sites’ GB 50194, regarding the installation of synchronization devices for parallel generators and the conditions for operating generators in parallel. 7 Distribution Lines 7.1 Overhead Lines 7.1.1 This section complies with the provisions of the current **standard, ‘Design Code for Overhead Power Lines of 66 kV and Below’ GB 50061. 7.1.2 This clause is in line with the provisions of the current standards, namely the \"Design Code for Overhead Power Lines of 66 kV and Below\" GB 50061 and the \"Safety Code for Power Supply and Use at Construction Sites\" GB 50194. Taking into account the actual conditions at construction sites, it emphasizes that dedicated utility poles should be used for overhead lines. 7.1.3 This section, in accordance with the current **standard \"Code for Design of Low-Voltage Power Distribution\" GB 50054 and taking into account the characteristics of electrical installations at construction sites, specifies the criteria for selecting the cross-sectional area of overhead line conductors as well as the minimum allowable values for such cross-sectional areas. 7.1.4 This clause is in line with the provisions of the current standards, namely the \"Design Code for Overhead Power Lines of 66 kV and Below\" GB 50061 and the \"Safety Code for Power Supply and Consumption at Construction Sites\" GB 50194, regarding the limitation on the number of conductor joints in overhead lines. The purpose is to prevent wire breaks, the subsequent collapse of utility poles due to those breaks, wires falling to the ground, as well as poor electrical contact, which could affect the safety and reliability of power supply. 7.1.5 This clause complies with the provisions of the current industry standard, the \"Code for Electrical Design of Civil Buildings\" JGJ/T 16, regarding the phase sequence arrangement of low-voltage overhead lines; taking into account the use of TN-S systems, uniform regulations on the installation location of the PE wire have been added. Sections 7.1.6 to 7.1.8 comply with the general provisions of the current **standard \"Code for Design of Overhead Power Lines of 66 kV and Below\" GB 50061; taking into account the characteristics of temporary power supply systems at construction sites, they specify the material and size requirements for the crossarms of overhead lines. 7.1.9 This clause is in line with the general provisions of the current **standard \"Code for Design of Overhead Power Lines of 66 kV and Below\" GB 50061; considering the poor environmental conditions at the construction site, some requirements are slightly higher than those specified in this standard. Points 7.1.10 and 7.1.11 are in line with the provisions of the current **standard, ‘Code for Safety of Power Supply and Use at Construction Sites’ GB 50194. 7.1.12 This clause is in accordance with the provisions of the current industry standard, the \"Code for Electrical Design of Civil Buildings\" JGJ/T 16. 7.1.13 It shall comply with the provisions of the current **standard, ‘Design Code for Overhead Power Lines of 66 kV and Below’ GB 50061. Points 7.1.14 and 7.1.15 are in line with the provisions of the current **standard \"Code for Safety of Power Supply and Consumption at Construction Sites\" GB 50194, as well as the current industry standard \"Code for Electrical Design of Civil Buildings\" JGJ/T 16. 7.1.16 This clause is in line with the relevant provisions of the current industry standard, the \"Code for Electrical Design of Civil Buildings\" JGJ/T 16. Taking into account the practice of installing strong-current and weak-current circuits on the same pole at construction sites, it specifies additional requirements regarding the spacing between overhead service lines and broadcast and telephone lines when they are laid together. Points 7.1.17 and 7.1.18 are in line with the principles set out in the current **standard \"Code for Design of Low-Voltage Power Distribution\" GB 50054 and the current industry standard \"Code for Electrical Design of Civil Buildings\" JGJ/T 16, by providing a slight additional safety margin for the protected power distribution circuits. 7.2 Cable Lines 7.2.1 This section complies with the current **standard \"Code for Design of Cables in Electrical Engineering\" GB 50217, as well as the current **standard \"Polyvinyl Chloride Insulated Cables with Rated Voltage of 450/750V and Below – Part 1: General Requirements\" GB 5023.1 (which is equivalent to IEC Standard IEC 227-1:1993 Amendment No.1 1995), and the current **standard \"Rubber Insulated Cables with Rated Voltage of 450/750V and Below – Part 1: General Requirements\" GB 5013.1 (which is equivalent to IEC Standard IEC 245-1:1994) regarding the requirements for cable conductors. Sections 7.2.2 to 7.2.4 are in accordance with the provisions of the current **standard, the ‘Code for Design of Cables in Electrical Engineering’ GB 50217. Sections 7.2.5 to 7.2.8 are in line with the principles set out in the current **standard \"Code for Design of Low-Voltage Power Distribution\" GB 50054 and the current industry standard \"Code for Electrical Design of Civil Buildings\" JGJ/T 16, by providing a slight additional safety margin for the protected power distribution circuits. 7.2 Cable Lines 7.2.1 This section complies with the current **standard “Code for Design of Cables in Electrical Engineering” GB 50217, as well as the current **standard “Polyvinyl Chloride Insulated Cables with Rated Voltage of 450/750V and Below – Part 1: General Requirements” GB 5023.1 (which is equivalent to IEC standard IEC 227-1:1993 Amendment No. 1995), and the current **standard “Rubber Insulated Cables with Rated Voltage of 450/750V and Below – Part 1: General Requirements” GB 5013.1 (which is equivalent to IEC standard IEC 245-1:1994) regarding the requirements for cable conductors. Sections 7.2.2 to 7.2.4 are in compliance with the provisions of the current **standard, the ‘Code for Design of Electrical Cables’ GB 50217. Sections 7.2.5 to 7.2.8 are in compliance with the current **standard \"Code for Design of Cables in Electrical Engineering\" GB 50217 and the current industry standard \"Code for Electrical Design of Civil Buildings\" JGJ/T 16. Among them, the higher requirements for the distance between buried cables and nearby external power cables as well as ducts are intended to ensure the safety of their installation. Furthermore, to meet the actual needs of the construction site and facilitate the inspection and maintenance of cable connectors, it is emphasized that these connectors should be placed in dedicated junction boxes on the ground. Articles 7.2.9 and 7.2.10 are formulated in accordance with the current standards such as the \"Code for Design of Cables in Electrical Engineering\" GB50217, the \"Code for Design of Low-Voltage Distribution Systems\" GB50054, the \"Code for Safety of Power Supply and Consumption at Construction Sites\" GB50194, as well as the industry standard \"Code for Electronic Design in Civil Buildings\" JGJ/T 16; they aim to take into account the actual conditions at construction sites and ensure the safe and reliable operation of cable systems. Among them, it is strictly prohibited to lay overhead cables along the scaffolding, and it is also forbidden for them to pass through the scaffolding; this is to prevent the scaffolding from becoming electrified due to mechanical damage to the cables. The measures to protect the power cables in the decoration and fitting section from mechanical damage and electrical hazards, by laying them along the floor at wall corners, involve using methods such as enclosing them in flame-retardant insulated tubes or cable trays. 7.3 Indoor Wiring Sections 7.3.1 to 7.3.3 comply with the provisions of the current **standard \"Code for Design of Low-Voltage Power Distribution\" GB 50054 and the current industry standard \"Code for Electrical Design of Civil Buildings\" JGJ/T 16. The term “indoor” as used here refers to the interior of all temporary facilities at the construction site, such as those used for office work, production, and living. Points 7.3.4 and 7.3.5 are in line with the current industry standard, the \"Code for Electrical Design of Civil Buildings\" JGJ/T 16; the requirements regarding the minimum cross-sectional area of insulated wires are slightly higher in this standard. 7.3.6 This clause is formulated in accordance with the current industry standard, the \"Code for Electrical Design of Civil Buildings\" JGJ/T 16. It sets slightly higher requirements for fixing wires using porcelain insulators, and adds additional requirements for fixing wires using porcelain clamps. 8 Distribution Boxes and Switch Boxes 8.1 Installation of Distribution Boxes and Switch Boxes 8.1.1–8.1.4 To comprehensively accommodate the sectional layout of electrical equipment at construction sites as well as their specific power usage patterns, and to enhance the safety and reliability of electricity supply, these four provisions, in accordance with the current **standard “Code for Design of Power Supply and Distribution Systems” GB 50052, specify the principles for three-level power distribution at construction sites, the requirement that each machine be equipped with its own switch and leakage protector within a separate box, and the principle of separating power distribution for mechanical equipment from that for lighting. The requirement for balanced three-phase loads is primarily aimed at reducing the asymmetry and voltage deviation in three-phase low-voltage distribution systems, thereby ensuring the quality of electrical power supplied. Articles 8.1.5 and 8.1.6, in accordance with the current standards **\"Guidelines for Electrical Safety\" GB/T 13869 and \"Safety Regulations for Power Supply and Use at Construction Sites\" GB 50194, and taking into account the conditions of work at construction sites, establish relevant restrictive provisions regarding the environmental conditions surrounding the installation locations of distribution boxes and switch boxes, in order to ensure their safe and reliable operation. 8.1.7 This clause specifies the unified material standards for distribution boxes and switch boxes, including a prohibition on the use of wooden distribution boxes and wooden switch boxes. 8.1.8 This clause is in accordance with the relevant provisions of the current standards **\"Code for Safety of Power Supply and Use at Construction Sites\" GB 50194 and \"Code for Design of Low-Voltage Distribution Systems\" GB 50054. To facilitate operation and maintenance, prevent damage from debris and splashed water on the ground, and adapt to the working conditions at construction sites, regulations have been set for the installation height of distribution boxes and switch boxes. 8.1.9～8.1.17 In accordance with the relevant provisions of the current standards such as the \"Guidelines for Electrical Safety\" GB/T 13869, the \"Safety Regulations for Power Supply and Use at Construction Sites\" GB 50194, and the \"Design Code for Low-Voltage Distribution Systems\" GB 50054, these 9 clauses establish comprehensive standardized requirements for the structural design of distribution boxes and switch boxes, in order to meet the conditions of outdoor work at construction sites as well as the needs related to zero-grounding protection in electrical systems. Among them, the installation dimensions of electrical appliances inside the enclosure are determined in accordance with the current **standard \"Insulation coordination of equipment in low-voltage systems – Part 1: Principles, requirements and tests\" GB/T 16935.1 (idt IEC 664-1:1992), as well as the requirements regarding electrical clearance and creepage distance specified in the \"Guidelines for the safe design of electrical equipment\" GB 4064. These dimensions are set taking into account the needs for convenient installation, maintenance, and operation of the electrical appliances. 8.2 Selection of electrical equipment 8.2.1 This clause complies with the provisions of the current **standard, ‘Guidelines for Electrical Safety’ GB/T 13869. 8.2.2 This section sets out comprehensive and standardized requirements for the electrical equipment in the main distribution box, in accordance with the general provisions of the current **standard \"Code for Design of Low-Voltage Power Distribution\" GB 50054, and taking into account the needs of temporary power supply systems at construction sites regarding power isolation as well as protection against short circuits, overloads, and electric leakage. Among them, the isolation device used as an isolating switch can be a knife-type switch or an isolation plug; it can also be a circuit breaker that features a clearly visible breaking point when it interrupts the circuit, such as the DZ20 series of circuit breakers with transparent plastic housings. These circuit breakers have transparent plastic covers through which the breaking point can be seen, and they can thus serve as isolating switches as well, eliminating the need for a separate isolating switch. Circuit breakers that do not have a clearly visible disconnection point when disconnected cannot be used as isolating switches. 8.2.3 This clause is in compliance with the current **standard \"Design Code for Electrical Measuring Instruments in Power Installations\" GBJ 63 and the current industry standard \"Code for Electrical Design of Civil Buildings\" JGJ/T 16. The prohibition against an open circuit in the secondary circuit of current transformers is intended to prevent the risk of electric shock caused by high voltages that may occur when the secondary circuit is open during operation. 8.2.4 This clause is in line with the current **standard \"Code for Design of Low-Voltage Power Distribution\" GB 50054. It meets the requirements for isolating, controlling the branch circuits of power distribution systems, as well as providing protection against short circuits and overloads. It also ensures safety and convenience during operation and maintenance; leakage protection devices are not required to be installed in distribution boxes. Sections 8.2.5 to 8.2.7 meet the requirements of the current standards **GB 50054 – Code for Design of Low-Voltage Power Distribution Systems**, GB 50055 – Code for Design of Power Supply Systems for General Electrical Equipment, and GB 13955 – Installation and Operation of Residual Current Devices; they are suitable for ensuring power isolation for electrical equipment as well as providing protection against short circuits, overloads, and residual currents. Among them, isolation appliances used as isolating switches refer to switch-blades, knife fuses, circuit breakers, and other electrical devices that can simultaneously disconnect all poles of the power supply and have a clearly visible breaking point when breaking the circuit. When appliances such as knife fuses or circuit breakers that have a visible breaking point are used and also possess overcurrent protection functions, it is not necessary to install separate overcurrent protection devices such as fuses or circuit breakers. Sections 8.2.10 to 8.2.14 comply with the provisions of the current standards **“General Requirements for Residual Current Devices” GB 6829, “Installation and Operation of Leakage Protection Devices” GB 13955, and “Effects of Electric Current on the Human Body – Part 1: Common Parts” GB/T 13870.1. Among them, the determination of the safety limit value of 30mA•s in clause 8.2.11 is primarily based on the current **standard \"Effects of electric current on the human body – Part 1: General aspects\" GB/T 13870.1, which specifies the time/current effect regions for sinusoidal alternating currents in the range of 1＜15～100Hz in China. 8.2.15 This clause is formulated in accordance with the current **standard ‘Guidelines for Electrical Safety’ GB/T 13869, taking into account the conditions of outdoor work at construction sites. It is strictly prohibited to use plugs and sockets for the movable connection of power supply leads, mainly to prevent accidental short circuits that could occur if a plug comes into contact with live electricity and falls off, as well as to avoid electric shock hazards resulting from direct human contact. 8.3 Use and Maintenance 8.3.1 This section specifies the names, purposes, and circuit divisions of distribution boxes and switch boxes in accordance with the current **standard \"Code for Safety of Power Supply and Consumption at Construction Sites\" GB 50194, primarily to prevent misoperations. Sections 8.3.2 to 8.3.4 are provisions established in accordance with the current **standard \"Guidelines for Electrical Safety\" GB/T 13869, taking into account the actual environmental conditions at construction sites, in order to ensure the safe operation of distribution boxes as well as the safety of maintenance activities. Among them, the regular inspection and maintenance intervals should not exceed one month. 8.3.5 This clause is in line with the general safety procedures for shutting down and restarting power supply in electrical systems, ensuring that the main distribution box and distribution panels remain in an unloaded state under normal conditions. 8.3.6 This clause is formulated in accordance with the current standards, namely the «Guidelines for Electrical Safety» GB/T 13869 and the «Safety Regulations for Power Supply and Use at Construction Sites» GB 50194, taking into account the actual conditions at construction sites. This includes turning off and locking the power switch box during lunch breaks, after work, or in cases of partial shutdowns lasting more than 1 hour, in order to prevent the equipment from being started accidentally. 8.3.7 This clause is formulated in accordance with the requirements of the current **standard, the ‘Safety Code for Power Supply and Use at Construction Sites’ GB 50194, regarding the knowledge and skills needed by personnel engaged in electrical work, and takes into account the actual conditions at construction sites. Articles 8.3.8 and 8.3.9 are stipulated in accordance with the current **standard \"Guidelines for Electrical Safety\" GB/T 13869, aiming to ensure the safe and reliable operation of distribution boxes and switch boxes, as well as to prevent the disruption of the three-level power distribution system and the requirement that each machine be equipped with its own switch, leakage protector, and box. Articles 8.3.10 and 8.3.11 are formulated in accordance with the current standards **\"Code for Design of Low-Voltage Power Distribution Systems\" GB 50054, \"Guidelines for Electrical Safety\" GB/T 13869, and the current industry standard \"Safety Regulations for Electric Power Construction\" DL 5009.2; they aim to ensure the proper electrical functioning of distribution boxes and switch boxes, as well as to protect their incoming and outgoing wires and connections from damage. 9 Electric construction machinery and hand-held electric tools 9.1 General provisions 9.1.1 These provisions are formulated in accordance with the current **standard \"Guidelines for Electrical Safety\" GB/T 13869, to establish common safety technical requirements for electric construction machinery and hand-held electric tools used in outdoor working conditions at construction sites. 9.1.2 This clause is formulated in accordance with the current **standard \"Code for Safety of Power Supply and Consumption at Construction Sites\", GB 50194, and specifies comprehensive grounding measures that take into account the requirements for neutral grounding protection for large-scale mechanical equipment, lightning protection and grounding, as well as repeated grounding of the PE wire. 9.1.3 This clause is in line with the provisions of the current **standard \"Safety of hand-held electric tools – Part 1: General requirements\" GB 3883.1 (which is equivalent to the International Electrotechnical Commission standard IEC 745-1) regarding the fact that for Class II and Class III tools, protection against electric shock relies primarily on double insulation (reinforced insulation) and supply at safely low voltage (SELV). 9.1.4 This clause is in line with the current **standard \"Code for Design of Cables in Electrical Engineering\" GB 50217, and meets the requirements of the TN-S neutral protection system. Three-phase electrical equipment is equipped with single-phase appliances; for example, indicator lights are single-phase appliances. 9.1.5 This clause is in compliance with the current **standard, the Code for Design of Power Distribution of General Electrical Equipment GB 50055. 9.2 Lifting Machinery 9.2.2 This clause complies with the current **standard \"Code for Construction and Acceptance of Electrical Installations in Lifting Machinery\" GB 50256, the \"Safety Regulations for Tower Cranes\" GB 5144, as well as the current industry standard \"Safety Regulations for Power Construction\" GB 5009. 9.2.4 This clause is formulated in accordance with the current **standard, the ‘Code for Safety of Power Supply and Use at Construction Sites’ GB 50194. Sections 9.2.5 to 9.2.7 are in line with the provisions of the current **standard, the Safety Regulations for Tower Cranes GB 5144. Among them, the insulation and grounding measures for preventing electromagnetic wave induction are primarily aimed at protecting people from electric shock. 9.2.8～9.2.12 The safe operation of outdoor elevators relies, in terms of electricity, on advanced electrical control technologies and mechanical-electrical interlock devices; relevant provisions have been made in these clauses to address this matter. 9.3 Pile-driving Machinery 9.3.1 This section complies with the current **standard \"Protection Degrees for Enclosures (IP Code)\” GB 4208. An IP68 protection level represents the highest level of protection against the entry of solid particles (dust-proof) and against the harmful effects of water intrusion (continuous submersion), and it is suitable for the operating conditions of motors in submersible drilling machines. 9.3.2 The provisions of this section refer to selecting the cable model in accordance with the current **standards (i.e., the International Electrotechnical Commission standard IEC 245-1:1994 \"Rubber-insulated cables for rated voltages up to 450/750 V – Part 1: General requirements\" and Appendix C of GB 5013.1), in order to suit the operating conditions of submersible motors. 9.3.3 These provisions specify the requirements for leakage protection under the working conditions of submersible drilling machines. 9.4 Ramming Machinery 9.4.1 The provisions of this section apply to ramming machinery that may operate in humid environmental conditions. 9.4.2 This clause is designed to accommodate the high-vibration operating conditions of ramming machinery, thereby enhancing the reliability of the electrical connection between the PE wire and the metal casing of the ramming machinery. 9.4.3 Same as the explanation in clause 9.3.2. 9.4.4 and 9.4.5: Earthfilling machinery generates intense vibrations during operation, causing the cables to move as well; this increases the risk of electric leakage as well as damage or breakage of the cables. The purpose of these provisions is to enforce proper insulation measures and operating procedures for operators, thereby preventing accidental electric shocks. The requirement that the cable length should not exceed 50m refers to the limitation on the size of the work area when the ramming machine is operating around its switch box. 9.5 Welding Equipment 9.5.1 This clause complies with the current **standard \"Code for Safety of Power Supply and Use at Construction Sites\" GB 50194 and the current industry standard \"Safety Regulations for Electric Power Construction\" DL 5009.2. Considering that welding sparks may ignite flammable and explosive materials and cause fires, these regulations include requirements for removing such flammable and explosive materials from the area around the welding site. Clauses 9.5.2 to 9.5.5 are in line with the provisions of the current standards **\"Code for Design of Power Distribution of General Electrical Equipment\" GB 50055 and \"Code for Safety of Power Supply and Use at Construction Sites\" GB 50194. In AC welding machines, in addition to installing a primary-side leakage protector in the switch box, a shock protection device must also be installed on the secondary side, in order to prevent electric shock hazards that may arise from the secondary-side no-load voltage of the welding machine. Currently, JZ-type arc welder electric shock protectors are widely used at construction sites; they can provide electric shock protection for both the primary and secondary sides. 9.6 Handheld electric tools Sections 9.6.1 to 9.6.4 are in line with the current **standard (namely the International Electrotechnical Commission standard IEC 745-1) ‘Safety of handheld electric tools – Part 1: General requirements’, GB 3883.1, as well as the current **standards ‘Safety technical regulations for the management, use, inspection, and maintenance of handheld electric tools’ GB 3787 and ‘Guidelines for electrical safety’ GB/T 13869. Narrow spaces refer to places such as boilers, metal containers, sewers, and pipes. The electric shock protection of Class I equipment relies not only on basic insulation but also includes a protective neutral or grounding measure, ensuring that exposed conductive parts do not become live in the event of damage to the basic insulation. The electric shock protection of Class II equipment relies not only on basic insulation but also includes additional double insulation or reinforced insulation; it does not provide protective earthing or grounding, nor is it dependent on the conditions of the equipment, and the enclosure is marked with a “⚪” symbol. Class II tools are further divided into two types: Class II tools with insulated material enclosures and Class II tools with metal material enclosures. The electric shock protection of Class III tools relies on safe extra-low voltage power supply, with no voltage higher than the safe extra-low voltage being generated within the tool. 9.7 Other electric construction machinery 9.7.1 This section complies with the current industry standard \"Technical Regulations for Safety in the Use of Construction Machinery\" JGJ 33, and meets the requirements regarding the installation of leakage protectors for the various electric machines listed, in their respective operating environments. 9.7.2 This clause is formulated in accordance with the current **standard \"Cables with rubber insulation, rated voltage 450/750 V – Part 1: General requirements\" GB 5013.1 (which is equivalent to the International Electrotechnical Commission standard IEC 245-1:1994), so as to ensure that the performance of the cables used meets the requirements of the operating environment conditions of various electric machinery. 9.7.3 This clause meets the requirements of the current industry standard, the \"Technical Regulations for Safety in the Use of Construction Machinery\" JGJ 33. 10 Lighting 10.1 General Provisions 10.1.1 This section complies with the current **standard \"Code for Design of Building Lighting\" GB 50034, and is suitable for the lighting requirements at construction sites. 10.1.2 In accordance with the current **standard ‘Code for Design of Building Lighting’ GB 50034, the lighting fixtures selected shall meet the requirements of high reliability during construction, the need to avoid frequent switching on and off, and energy efficiency. 10.1.3 This clause is in compliance with the current **standard \"Code for Design of Building Lighting\" GB 50034 and the current industry standard \"Code for Design of Urban Road Lighting\" GJJ45. 10.1.4 This clause complies with the requirements in the current **standard ‘Guidelines for Electrical Safety’ GB/T 13869 regarding the verification of the integrity of general electrical installations prior to their use. 10.1.5 The individual lighting power supply plan specified in this clause may be prepared in accordance with the requirements of this chapter and taking into account the actual conditions on site. 10.2 Lighting Power Supply 10.2.1 In accordance with the relevant provisions of the current **standard, the ‘Code for Design of Building Lighting’ GB 50034, and taking into account the environmental conditions of various lighting areas at construction sites, this section sets specific restrictions on the voltage required for lighting supply in different types of areas. 10.2.2, 10.2.3 These clauses are in accordance with the current **standard \"Code for Design of Building Lighting\" GB 50034. Taking into account the mobility and exposure of field lights as secondary lighting sources, restrictive provisions are set for their supply voltage and lamp structure in order to prevent accidents such as accidental electric shock or electrical fires caused by defects in the lamps. Safe extra-low voltage refers to a voltage in a circuit isolated from the power supply by a safe isolation transformer, where the AC effective value between conductors or between any conductor and ground does not exceed 50 V, or the DC ripple value does not exceed a certain limit. The DC ripple value is provisional. In cases with special requirements, especially when direct contact with live parts is permitted, a maximum voltage limit of 50 V below the RMS value for AC or the pulsating value for DC can be specified. This voltage limit should not be exceeded, whether the device is loaded or unloaded. 10.2.4 This clause is in compliance with the current **standard, the ‘Design Standard for Building Lighting’ GB 50034. 10.2.5 This clause is in line with the provisions of the current **standard, the ‘Safety Code for Power Supply and Use at Construction Sites’ GB 50194, regarding portable lamp transformers. It also emphasizes the prohibition of using autotransformers, as there is an electrical connection between their primary and secondary windings; moreover, since the voltage on the secondary side can be adjusted, this can lead to unstable voltage levels. In addition, winding failures can cause the higher voltage on the primary side to be transmitted to the secondary side, resulting in the destruction of lamps and electric shock. 10.2.6 This clause is in accordance with the provisions of the current **standard, the ‘Design Code for Building Lighting’ GB 50034. 10.2.7 This clause is formulated in accordance with the current standards, namely the **Guidelines for Electrical Safety GB/T 13869 and the Code for Safety of Power Supply and Use at Construction Sites GB 50194. The length of the power cable on the primary side of the transformer should not exceed 3 meters, mainly to keep it close to the switch box for easier operation and control. 10.2.8 This clause is in line with the relevant provisions of the current **standards such as the \"Code for Design of Building Lighting\", GB 50034, the \"Code for Design of Low-Voltage Power Distribution\", GB 50054, and the current industry standard the \"Code for Electrical Design of Civil Buildings\", JGJ/T 16. 10.3 Lighting fixtures 10.3.1 This clause complies with the principles specified in the current **standard \"Guidelines for Electrical Safety\" GB/T 13869, and is in line with the requirements regarding neutral grounding protection and leakage protection for electrical equipment as stipulated in Chapter 8 of these specifications. 10.3.2 The provisions in this clause regarding the installation height of indoor and outdoor lighting fixtures, as well as the safe distance between these fixtures and flammable materials, are in line with the current standards **“Safety Code for Power Supply and Use at Construction Sites” GB 50194 and “Standard for Lighting Design in Buildings” GB 50034. 10.3.3 This clause is in compliance with the current **standards, namely the «Code for Design of Building Lighting» GB 50034 and the «Code for Acceptance of Construction Quality of Building Electrical Engineering» GB 50303. 10.3.4 This provision is formulated in accordance with the current **standard, the ‘Code for Design of Building Lighting’ GB 50034. Since the electromagnetic ballasts used with fluorescent lamps generate heat during operation, this provision is intended primarily to prevent flammable materials from catching fire in the event that the ballast overheats or gets damaged due to a short circuit. Clauses 10.3.5 and 10.3.6 are in line with the provisions of the current **standard, the ‘Code for Construction and Acceptance of Electrical Lighting Installations in Electrical Equipment Installation Projects’ GB 50259. 10.3.7 This clause is in compliance with the provisions of the current **standards, namely the ‘Guidelines for Electrical Safety’ GB/T 13869 and the ‘Code for Construction and Acceptance of Electrical Lighting Installations in Electrical Equipment Installation Projects’ GB 50259. Articles 10.3.8 and 10.3.9 are formulated in accordance with the current standard \"Code for Construction and Acceptance of Electrical Lighting Installations in Electrical Equipment Installation Projects\" GB 50259, to address the lighting conditions in outdoor construction sites as well as the safety control requirements for temporary lighting installations. 10.3.10 This clause is in compliance with the current **standard \"Code for Safety of Power Supply and Use at Construction Sites\" GB 50194 and the current industry standard \"Safety Work Procedures for Electric Power Construction\" DL 5009.2. 10.3.11 This provision primarily emphasizes the need to install night-time warning lighting for tall construction projects that pose a risk to external safety at the construction site, as well as for construction machinery and areas where trenches or foundations are being dug. It also requires that the power supply for such warning lighting be reliable. The use of red warning lights is in accordance with the provisions of the current **standard ‘Safety Colors’ GB 2893**
Contributing units to this standard: Building Safety Branch of China Construction Industry Association, Shanghai Construction Safety Association, Shandong Provincial Construction Safety Supervision Station, Jiangsu Provincial Building Safety and Equipment Management Association, Anhui Provincial Construction Industry Safety Association, Yunnan Provincial Construction Project Safety Supervision Station, Wuhan Urban and Rural Work Safety Management Station, Shaanxi Provincial Construction Project Quality and Safety Supervision Station, Yantai Construction Safety Supervision Station, Liaoning Provincial Department of Construction, Fushun Municipal Engineering Quality and Safety Supervision Station
Main drafters of this standard: Xu Rongjie, Qin Chunfang, Kong Jinqiang, Li Yin, Wu Xiuli, Gu Jiansheng, Liu Shicai, Zhang Ming, Pu Yufeng, Cao Xianping, Bian Erlun, Wang Xiaobo, Liu Shaofei, Li Changkai, Bai Bo
Table of Contents
1 General Provisions
2 Terms and Codes
2.1 Terms
2.2 Codes
3 Management of Temporary Electricity Use
3.1 Design for Temporary Electricity Use
3.2 Electricians and Personnel Using Electricity
3.3 Safety Technical Records
4 Protection of External Power Lines and Electrical Equipment
4.1 Protection of External Power Lines
4.2 Protection of Electrical Equipment
5 Grounding and Lightning Protection
5.1 General Provisions
5.2 Protective Zero Connection
5.3 Grounding and Ground Resistance
5.4 Lightning Protection
6 Distribution Rooms and Self-Provided Power Sources
6.1 Distribution Rooms
6.2 230/400V Self-Provided Generator Sets
7 Distribution Lines
7.1 Overhead Lines
7.2 Cable Lines
7.3 Indoor Wiring
8 Distribution Boxes and Switch Boxes
8.1 Installation of Distribution Boxes and Switch Boxes
8.2 Selection of Electrical Devices
8.3 Use and Maintenance
9 Electric Construction Machinery and Handheld Electric Tools
9.1 General Provisions
9.2 Lifting Machinery
9.3 Pile Driving Machinery
9.4 Earthmoving Machinery
9.5 Welding Machinery
9.6 Handheld Electric Tools
9.7 Other Electric Construction Machinery
10 Lighting
10.1 General Provisions
10.2 Lighting Power Supply
10.3 Lighting Fixtures
Appendix A Average Annual Number of Thunderstorm Days in China
Appendix B Ball-rolling Method
Appendix C Motor Load Lines and Selection of Electrical Devices
Explanation of Terms Used in This Standard
Explanations of Articles
1 General Provisions
1.0.1 This standard is formulated to implement laws and regulations on work safety, ensure electrical safety at construction sites, prevent electric shock and electrical fires, and promote the development of the construction industry. 1.0.2 These specifications apply to the design, installation, use, maintenance, and demolition of low-voltage power systems with a 220/380V three-phase four-wire system and directly grounded neutral point, used in temporary electrical installations at construction sites for new, renovated, and expanded industrial and civil buildings as well as municipal infrastructure projects. 1.0.3 A 220/380V three-phase four-wire low-voltage power system with the neutral point directly grounded, designed specifically for temporary electrical use at construction sites, must comply with the following requirements: 1 A three-level power distribution system shall be employed ； 2 Adopt a TN-S neutral protection system ； 3 A two-stage leakage protection system is adopted. 1.0.4 For temporary power use at construction sites, in addition to complying with the provisions of these specifications, it is also necessary to meet the requirements of **current relevant mandatory standards. 2 Terms and Codes 2.1 Terms 2.1.1 Low voltage Voltage with an AC rated voltage of 1 kV or less. 2.1.2 High voltage: A voltage with an AC rated voltage of 1 kV or more. 2.1.3 External circuit: Electrical circuits other than those in the distribution network for temporary power supply at the construction site. 2.1.4 Construction sites with electrostatic fields These are construction sites where harmful static electricity can be generated as a result of friction, compression, induction, and poor grounding, posing risks to both humans and the environment. 2.1.5 Source of powerful electromagnetic waves: An electromagnetic radiator whose radiant waves can induce harmful voltages with respect to the ground in the mechanical equipment at the construction site. 2.1.6 Ground connection A part of the equipment is used to establish a conductive path to the earth. 2.1.7 Working ground connection A grounding connection that is necessary for circuits or equipment to meet their operational requirements, such as the grounding of the low-voltage neutral point of transformers and the neutral point of generators. 2.1.8 Iterative ground connection: A grounding method in which one or more points on the equipment’s grounding wire are reconnected to the earth through grounding devices. 2.1.9 Earth lead A metal conductor that is buried in the ground and in direct contact with the earth. 2.1.10 Manual grounding A grounding electrode that is manually buried in the ground. 2.1.11 Natural grounding: Components that have been buried in the ground prior to construction and can be used as grounding elements, such as the rebar structure of reinforced concrete foundations, metal well pipes, and metal pipelines (other than those for gas). 2.1.12 Ground line: A metal conductor that connects the metal structure of the equipment to the grounding electrode (including the connection bolts). 2.1.13 Grounding device: The combination of the grounding electrode and the grounding wire. 2.1.14 Ground resistance: The resistance of the grounding system relative to the ground. It is the sum of the resistance of the grounding wire, the resistance of the grounding electrode, the contact resistance between the grounding electrode and the soil, and the stray resistance in the soil. The ground resistance can have an approximate value determined by calculation or measurement; this value equals the ratio of the voltage of the grounding device with respect to the ground to the current flowing into the ground through that grounding device. 2.1.15 Power frequency ground resistance: The ground resistance determined based on the power frequency current that flows into the ground through the grounding device. 2.1.16 Shock ground resistance: The ground resistance determined based on the impulse current (simulating lightning current) that flows into the ground through the grounding system. 2.1.17 Electrical connection: A connection that provides a direct electrical path between conductors (with contact resistance close to zero). 2.1.18 Live-part: A conductor or conductive part that is energized during normal operation. It includes the neutral conductor (neutral wire), but does not include the protective conductor (protective neutral wire or protective line). Conventionally, it also does not include wires (conductors) in which the working neutral wire and the protective neutral wire are combined. 2.1.19 Exposed conductive part: A touchable conductive part of an electrical equipment. It is not charged under normal conditions, but it may become charged in the event of a fault. 2.1.20 Electric shock: Current flowing through a human body or an animal’s body, causing pathophysiological effects. 2.1.21 Direct contact: Contact between the human body or livestock and live parts. 2.1.22 Indirect contact: Contact between the human body, livestock, and exposed conductive parts that become charged under fault conditions. 2.1.23 Distribution box: A device specifically used for distributing electricity, including the main distribution box and the distribution boxes; unless otherwise specified, the main distribution box and the distribution boxes are collectively referred to as distribution boxes. 2.1.24 Switch box: A general term for the final level of power distribution equipment; it can also serve as a control device for electrical equipment. 2.1.25 Isolating transformer: A transformer in which the input winding and the output winding are electrically isolated from each other, used to prevent the danger posed by accidental simultaneous contact with live parts (or metal components that may become live due to damaged electrical insulation) and the ground. 2.1.26 Safety isolating transformer: An isolating transformer that supplies power to safely low-voltage circuits. Its input winding and output winding are electrically separated by insulation equivalent to double insulation or reinforced insulation. It is designed specifically to provide a safe extremely low voltage for distribution circuits, tools, or other equipment. 2.2 Codes 2.2.1 DK——Power isolation switch ； 2.2.2 H——Lighting fixture ； 2.2.3 L1, L2, L3 —— the three phase wires of a three-phase circuit ； 2.2.4 M——Electric motor ； 2.2.5 N——Neutral point, neutral wire, working neutral wire ； 2.2.6 NPE —— A grounding wire with both neutral and protective functions, also known as protective neutral wire ； 2.2.7 PE — Protection neutral wire, protective wire ； 2.2.8 RCD — Residual current device, leakage circuit breaker ； 2.2.9 T——Transformer ； 2.2.10 TN – A neutral grounding protection system in which the exposed conductive parts of electrical equipment are connected to the ground through the neutral wire, when the power supply’s neutral point is directly grounded ； 2.2.11 TN-C —— A neutral protection system in which the working neutral and the protective neutral are combined ； 2.2.12 TN-C-S —— a neutral protection system in which the working neutral and the first part of the protective neutral are combined, while the latter part is separated ； 2.2.13 PN-S —— A neutral protection system in which the working neutral and the protective neutral are separated ； 2.2.14 TT – A grounding protection system in which the power supply neutral point is directly grounded, and the exposed conductive parts of electrical equipment are also directly grounded; the grounding point for electrical equipment is separate from the grounding point of the power supply neutral point ； 2.2.15 W——Welding machine. 3 Management of Temporary Electricity Use 3.1 Organizational Design for Temporary Electricity Use 3.1.1 When there are 5 or more temporary electricity devices at a construction site, or when the total capacity of these devices is 50 kW or more, an organizational design for electricity use must be prepared. 3.1.2 The temporary electrical power supply plan for the construction site shall include the following contents: 1 Site survey ； 2 Determine the locations of the power supply inlet, substation or distribution room, distribution equipment, electrical appliances, as well as the route of the electrical circuits ； 3 Perform load calculation ； 4 Select the transformer ； 5 Design of the power distribution system: 1) Design the power distribution lines, selecting wires or cables ； 2) Design the power distribution apparatus and select electrical equipment ； 3) Design the grounding device ； 4) Draw drawings for temporary power supply projects, which mainly include the general layout plan of the power supply system, the layout diagram of the distribution equipment, the wiring diagram of the distribution system, and the design diagram of the grounding system. 6 Design of lightning protection devices ； 7 Determine protective measures ； 8 Formulate safety measures for electrical use and electrical fire prevention measures. 3.1.3 Drawings for temporary power supply projects shall be prepared separately, and such projects shall be constructed in accordance with those drawings. 3.1.4 When preparing a design for temporary power use or making changes to it, the \"preparation, review, and approval\" procedures must be followed. It shall be prepared by electrical engineering technicians, reviewed by the relevant departments, and approved by the technical director of an enterprise with legal person status before implementation. Relevant drawing materials should be added when modifying the electrical design. 3.1.5 Temporary electrical installations must be jointly inspected and approved by the departments responsible for their preparation and review, as well as by the user unit; they can only be put into use after passing such inspection. 3.1.6 For construction sites where the number of temporary electrical equipment is 5 or less and the total capacity of such equipment is 50 kW or less, safety measures for electrical use and electrical fire prevention must be established, and these measures must comply with the provisions of paragraphs 3.1.4 and 3.1.5 of this standard. 3.2 Electricians and persons using electricity 3.2.1 Electricians must pass assessments in accordance with **current standards before they can work with a valid certificate ； Other electrical workers must undergo relevant training and technical briefings, and only after passing the assessments can they start working. 3.2.2 The installation, inspection, maintenance, or removal of temporary electrical equipment and circuits must be carried out by electricians, and supervision must be provided. The electrician’s level should be appropriate to the difficulty and technical complexity of the project. 3.2.3 All users of electrical equipment must possess basic knowledge of safe electricity use as well as an understanding of the capabilities of the equipment they are using. They must also comply with the following requirements: 1 Before using electrical equipment, it is necessary to wear and use the appropriate personal protective equipment as required, and the electrical installations and protective devices must be inspected; it is strictly prohibited to operate equipment that has defects ； 2 Maintain and care for the equipment used, and report any issues promptly for resolution ； 3 The switch box of a device that is to be temporarily shut down must have its power supply isolation switch disconnected, and the door must be closed and locked ； 4 When moving electrical equipment, it must be done after the electrician cuts off the power supply and takes proper precautions. 3.3 Safety Technical Records 3.3.1 Safety technical records must be established for temporary electricity use at construction sites, and these records should include the following contents: 1 Safety documents related to the electrical installation plan ； 2 Modify the materials for the electrical design plan ； 3 Electrical Technology Briefing Materials ； 4 Electrical Engineering Inspection and Acceptance Form ； 5 Test and inspection certificates for electrical equipment and commissioning records ； 6 Record Form for Measuring Ground Resistance, Insulation Resistance, and Leakage Operation Parameters of Leakage Circuit Breakers ； 7 Regular Inspection (Review) Table ； 8 Records of electrical work installation, inspection, maintenance, and demolition. 3.3.2 The safety technical records shall be established and managed by the electrical technician in charge of the site. Among these, the “records of electrical work installation, inspection, maintenance, and demolition” can be entrusted to an electrician for management; they must be reviewed and approved by the project manager on a weekly basis, and should be archived collectively after the temporary electrical installations are removed. 3.3.3 Temporary electrical installations should be inspected regularly. During regular inspections, the ground resistance value and insulation resistance value should be rechecked. 3.3.4 Regular inspections of temporary electrical installations should be carried out by section and in phases; any safety hazards must be addressed promptly, and re-inspection and acceptance procedures must be followed. 4 Protection of External Power Lines and Electrical Equipment 4.1 Protection of External Power Lines 4.1.1 Construction projects shall not carry out work, set up temporary shelters, build living facilities, or stack components, tools, materials, and other debris directly below external overhead power lines. 4.1.2 The minimum safe operating distance between the perimeter of the construction in progress (including scaffolding) and the edge of the external overhead power lines shall comply with the requirements specified in Table 4.1.2. Table 4.1.2 Minimum safe operating distance between the perimeter of construction projects (including scaffolding) and the edge of overhead power lines. Note: The ladders for ascending and descending from the scaffolding should not be located on the side where there are external power lines. 4.1.3 When the motor vehicle lane at the construction site intersects with overhead external power lines, the minimum vertical distance between the lowest point of the overhead lines and the road surface shall comply with the requirements specified in Table 4.1.3. Table 4.1.3 Minimum vertical distance when motor vehicle lanes and overhead lines intersect at the construction site 4.1.4 Cranes are strictly prohibited from operating above unprotected external overhead power lines. When lifting operations are carried out near external overhead power lines, the minimum safe distance between any part of the crane or the edge of the load, at its maximum tilt, and the edge of the overhead lines shall comply with the requirements specified in Table 4.1.4. Table 4.1.4 Minimum safe distance between cranes and the edge of overhead lines 4.1.5 The distance between the edge of the trench dug at the construction site and the edge of the trench for buried external electrical cables must be no less than 0.5 m. 4.1.6 When the requirements specified in paragraphs 4.1.2 to 4.1.4 of these specifications cannot be met, insulation isolation measures must be taken, and prominent warning signs shall be installed. When installing protective facilities, approval from the relevant authorities is required; temporary power shutdown of the circuit or other reliable safety measures must be employed, and the work must be supervised by electrical engineering technicians and dedicated safety personnel. The safety distance between protective facilities and external power lines shall not be less than the values specified in Table 4.1.6. The protective facilities should be sturdy and stable, and the isolation protection against external electrical lines should reach IP30 level. Table 4.1.6 Minimum safe distance between protective facilities and external power lines 4.1.7 When the protective measures specified in Article 4.1.6 of these specifications cannot be implemented, it is necessary to consult with the relevant authorities and take measures such as shutting down power supply, relocating external power lines, or changing the location of the project; construction is strictly prohibited without taking such measures. 4.1.8 When digging trenches near external overhead power lines, it is necessary to take reinforcement measures in conjunction with the relevant departments to prevent the poles of these overhead lines from tilting or falling over. 4.2 Protection of electrical equipment 4.2.1 Flammable and explosive substances, sources of contamination, and corrosive agents must not be stored around electrical equipment; if such substances are present, they must be removed or protected, and the level of protection required must be appropriate to the environmental conditions. 4.2.2 The location where electrical equipment is installed should be free from object impact and mechanical damage; otherwise, protective measures should be taken. 5 Grounding and Lightning Protection 5.1 General Provisions 5.1.1 In a TN-S neutral protection system powered by a dedicated transformer at the construction site, the metal enclosures of electrical equipment must be connected to the protective neutral wire. The protective neutral wire should be derived from the working ground wire, the neutral wire on the power side of the distribution room (main distribution panel), or the neutral wire on the power side of the main leakage protector (Figure 5.1.1). Figure 5.1.1 Schematic of TN-S neutral protection system when powered by a dedicated transformer 1 – Working ground ； 2－PE wire repeated grounding ； 3 – Metal enclosures of electrical equipment (exposed conductive parts that are not normally live) ； T-Transformer 5.1.2 When the construction site shares the same power supply system as external electrical lines, the grounding and neutral connection protection of electrical equipment shall be consistent with the protection of the original system. It is not allowed to use protective zero connection for some equipment while using protective grounding for other equipment. When using the TN system for protective earthing, the working neutral wire (N wire) must pass through the main residual current device, while the protective earth wire (PE wire) must be led out from the point where the supply neutral wire is re-earthed or from the side of the main residual current device connected to the power supply, thereby forming a local TN-S earthing protection system (Figure 5.1.2). Figure 5.1.2 Schematic diagram of the protective neutral conductor in a local TN-S neutral grounding system during three-phase four-wire power supply; 1 – Repeated grounding of the NPE conductor ； 2－PE wire repeated grounding ； L1, L2, L3 – phase wires ； N – Working neutral wire ； PE – Protective neutral wire ； DK – Main power isolation switch ； RCD – Main leakage protector (a circuit breaker that provides protection against short circuits, overloads, and leakage current). 5.1.3 In a TN system with neutral grounding, no further electrical connections shall be made between the working neutral wire and the protective neutral wire via the main leakage protector. 5.1.4 In a TN neutral-grounded protection system, the PE neutral wire shall be laid separately. The repeated grounding wire must be connected to the PE wire; it is strictly prohibited to connect it to the N wire. 5.1.5 When a safety isolation transformer is used, with the primary side powered by a neutral-grounded protection system having a voltage of 50V or higher and the secondary side having a voltage of 50V or lower, the secondary side shall not be grounded; furthermore, the secondary wiring shall be protected by insulated tubes or flexible wires with rubber sheaths. When a conventional isolation transformer is used, one end of its secondary side should be grounded, and the exposed conductive parts of the transformer that are not energized under normal conditions should be connected to the protective neutral wire of the primary circuit. The above transformers shall also be equipped with protection measures to prevent direct contact with live parts. 5.1.6 In the temporary electrical power system at the construction site, it is strictly prohibited to use the ground as a phase wire or neutral wire. 5.1.7 The installation of grounding devices shall take into account the effects of seasonal changes such as soil drying or freezing, and shall comply with the provisions in Table 5.1.7; the grounding resistance value shall meet the requirements of Section 5.3 of this code throughout all four seasons. However, the impulse grounding resistance value of lightning protection devices only takes into account the effect of dry soil conditions during the thunderstorm season. Table 5.1.7 Seasonal coefficient φ values for grounding devices Note: When the ground is relatively dry, use the smaller value from the table ； In relatively humid conditions, use the higher value from the table. 5.1.8 When the material used for the PE wire is the same as that of the phase wires and the working neutral wire (N wire), its minimum cross-sectional area shall comply with the provisions in Table 5.1.8. Table 5.1.8 Relationship between the cross-sectional area of the PE wire and that of the phase wires 5.1.9 The protective neutral wire must be made of insulated wire. The PE wire connecting the distribution device and the electric machinery shall be an insulated multi-strand copper wire with a cross-sectional area of not less than 2.5 mm2. The PE wire of handheld power tools should be insulated multi-strand copper wire with a cross-sectional area of not less than 1.5 mm2. 5.1.10 Switches or fuses must not be installed on the PE conductor; it must not carry operating current, and the wire must not be disconnected. 5.1.11 The color coding of the live wires, N wire, and PE wire must comply with the following regulations: the insulation colors for the live wires L1 (A), L2 (B), and L3 (C) in order are yellow, green, and red respectively ； The insulation color of the N wire is light blue ； The insulation color of the PE wire is green/yellow. Under no circumstances shall the aforementioned color codes be mixed or used interchangeably. 5.2 Protective Earthing 5.2.1 In a TN system, the exposed conductive parts that are not live in the following electrical equipment shall be connected to earth for protection: 1 The metal casings of motors, transformers, electrical appliances, lighting fixtures, and hand-held electric tools ； 2 Metal components of the drive mechanisms in electrical equipment ； 3 Metal frames of distribution cabinets and control cabinets ； 4 Metal enclosures, frames of distribution equipment, as well as metal fences and doors located near live parts ； 5 Metal protective tubes for power lines, steel cables for wiring, bases and tracks for cranes, metal working platforms for slipform construction, etc ； 6 The metal enclosures and supports of electrical devices such as switches and capacitors installed on power line poles (towers). 5.2.2 Electrical equipment in damp or particularly harsh-condition construction sites such as fortifications, civil air defense facilities, and tunnels must be equipped with protective zero connection. 5.2.3 In TN systems, the exposed conductive parts of the following electrical equipment that are not live do not require protection grounding: 1 The metal enclosures of electrical installations with an AC voltage of 380V or less in dry rooms with poorly conductive floors such as wood or asphalt (except in cases where maintenance personnel may come into contact simultaneously with both the metal enclosure of the electrical equipment and the grounded metal parts) ； 2 Electrical measuring instruments, current transformers, and the metal enclosures of electrical appliances that are installed on the metal frames of distribution cabinets, control cabinets, and distribution boxes, and are in reliable electrical connection with them. 5.3 Grounding and Ground Resistance 5.3.1 The working ground resistance value of power transformers or generators with a single unit capacity exceeding 100 kVA, or those operating in parallel using the same grounding system and having a total capacity exceeding 100 kVA, must not be greater than 4 Ω. The working ground resistance value of power transformers or generators with a single-unit capacity of no more than 100 kVA, or those operating in parallel using the same grounding system with a total capacity of no more than 100 kVA, must not be greater than 10 Ω. In areas where the soil resistivity is greater than 1000Ω•m, when it is difficult to achieve the aforementioned grounding resistance value, the working grounding resistance can be increased to 30Ω. 5.3.2 In a TN system, in addition to being repeatedly grounded at the distribution room or main distribution panel, the protective neutral wire must also be repeatedly grounded at intermediate points and at the end of the distribution system. In TN systems, the grounding resistance value of each repeated grounding device for the protective neutral wire should not exceed 10Ω. In power systems where the allowable value for the working ground resistance is 10Ω, the equivalent resistance value of all repeated grounds should not exceed 10Ω. 5.3.3 In TN systems, it is strictly prohibited to provide additional grounding for the separately laid working neutral wire. 5.3.4 The grounding wires of each grounding device shall consist of 2 or more conductors, which make electrical connections to the grounding electrode at different points. Aluminum conductors shall not be used as grounding electrodes or underground grounding wires. For vertical grounding electrodes, angle steel, steel pipes, or plain round steel should be used; deformed steel bars must not be employed. Grounding can utilize natural grounding electrodes, but their electrical connection and thermal stability must be ensured. 5.3.5 For electrical equipment powered by mobile generators, its metal enclosure or base shall be in reliable electrical connection with the generator’s grounding device. 5.3.6 The grounding of mobile generator systems shall meet the requirements for the grounding of power transformer systems. The following situations exempt the need for additional protective grounding: 1. When a portable generator and the electrical equipment it powers are mounted on the same metal frame, and no power is supplied to other devices. 2 Electrical equipment in a quantity not exceeding 2 units may be powered by a dedicated mobile generator, provided that the distance between the power supply equipment and the electrical equipment itself is no more than 50 meters, and there is a reliable electrical connection between the metal enclosures of both types of equipment. 5.3.7 In construction sites with static electricity, grounding and leakage measures should be taken for the static electricity accumulated on mechanical equipment. The grounding resistance value of the dedicated static grounding electrode in each group should not exceed 100Ω; in areas with high soil resistivity, it should not exceed 1000Ω. 5.4 Lightning Protection 5.4.1 In areas where the soil resistivity is below 200Ω•m, it may not be necessary to install a separate lightning protection grounding system for the utility poles; however, at the overhead incoming or outgoing connections in the distribution room, the insulator feet should be connected to the grounding system of the distribution room. 5.4.2 Mechanical equipment such as cranes, jib cranes, and gantry cranes on the construction site, as well as metal structures such as steel scaffolding and structures that are under construction, shall be equipped with lightning protection devices in accordance with the provisions of Table 5.4.2 when they are located outside the protection range of the lightning arresters of the lightning protection systems of adjacent buildings, structures, and other facilities. The average annual number of thunderstorm days (d) per region in Table 5.4.2 shall be determined in accordance with Appendix A of this code. When the protection range of the lightning rod (lightning conductor) on the highest mechanical equipment can cover other equipment, and that equipment is the last to be removed from the site, those other devices do not need to be equipped with lightning protection systems. The protection area of the lightning receptor in a lightning protection system can be determined using the rolling sphere method specified in Appendix B of this code. Table 5.4.2 Requirements for installing lightning protection devices on mechanical equipment and overhead structures at construction sites 5.4.3 The lightning protection down conductors for mechanical equipment or structures can utilize the metal framework of such equipment or structures, provided that an electrical connection is ensured. 5.4.4 The length of the lightning rods (lightning conductors) on mechanical equipment should be 1–2 m. Tower cranes do not require a separate lightning rod (lightning conductor). 5.4.5 For the mechanical equipment used to install lightning rods (lightning conductors), all fixed power, control, lighting, signaling, and communication cables should preferably be laid in steel pipes. The steel pipe and the metal structure of the mechanical equipment should be electrically connected. 5.4.6 The impulse grounding resistance value of all lightning protection devices at the construction site shall not exceed 30Ω. 5.4.7 For electrical equipment installed on machinery designed for lightning protection, the PE wire connected to such equipment must also be provided with a redundant grounding connection. The redundant grounding for the electrical equipment on the same machinery and the lightning protection grounding for the machinery can share the same grounding electrode, but the grounding resistance must meet the requirements specified for redundant grounding resistance. 6 Distribution Rooms and On-site Power Supplies 6.1 Distribution Rooms 6.1.1 Distribution rooms should be located near the power source, and in areas with low levels of dust and moisture, minimal vibration, no corrosive substances, no flammable or explosive materials, and good road access. 6.1.2 The ends of the arranged distribution cabinets and control cabinets shall be electrically connected to the repeated grounding wire and the protective neutral wire. 6.1.3 The distribution room and control room shall be capable of natural ventilation, and measures shall be taken to prevent rain, snow from entering as well as animals from getting in. 6.1.4 The layout of the distribution room shall meet the following requirements: 1 The width of the operation passage on the front side of the distribution cabinets shall be no less than 1.5 m when the cabinets are arranged in a single row or in two rows back to back, and no less than 2 m when they are arranged in two rows face to face ； 2 The width of the maintenance passage behind the distribution cabinet should be no less than 0.8 m when the cabinets are arranged in a single row or face to face in two rows; it should be no less than 1.5 m when arranged back to back in two rows. In areas where there are protrusions in the building structure, the width of the passage at such locations can be reduced by 0.2 m ； 3 The maintenance access width on the side of the distribution cabinet shall be no less than 1m ； 4 The distance between the top grid of the distribution room and the ground should be no less than 3m ； 5 When a duty or maintenance room is installed inside the distribution room, the horizontal distance between the edge of this room and the distribution cabinets should be greater than 1 m, and barriers should be used for separation ； 6 When the vertical distance between the exposed busbars in the switchgear room and the ground is less than 2.5 m, barriers shall be used for isolation, and the height of the passage beneath the barriers shall be not less than 1.9 m. 7 The clear distance between the upper edge of the distribution room fence and the live parts directly above it shall be not less than 0.075 m ； 8 The upper end of the distribution device should be at a distance of not less than 0.5m from the shed ； 9 The busbars in the distribution room are painted with colored paint to indicate the phase sequence ； Based on the front side of the cabinet, its coloring shall comply with the requirements specified in Table 6.1.4 ； The fire resistance rating of the buildings and structures in the 10 distribution rooms shall be no less than grade 3; sand boxes and fire extinguishers suitable for extinguishing electrical fires shall be installed inside ； Table 6.1.4 Busbar Coloring 11 The doors of the distribution room open outward and are equipped with locks ； 12 The lighting in the distribution room is equipped with both normal lighting and emergency lighting. 6.1.5 The distribution cabinet shall be equipped with a wattmeter, as well as ammeters and voltmeters. An ammeter and a metering electricity meter must not share the same set of current transformers. 6.1.6 The distribution cabinet shall be equipped with a power isolation switch as well as protective devices against short circuits, overloads, and electric leakage. When the power isolation switch is opened, there should be a clearly visible break point. 6.1.7 The distribution cabinets shall be numbered and marked with their purpose. 6.1.8 When performing maintenance on a distribution cabinet or distribution circuit during a power outage, grounding wires should be installed, and a sign stating “Do not close switch – work in progress” should be placed. The switching on and off of electricity must be handled by a designated person. 6.1.9 The distribution room should be kept clean, and no clutter that may hinder operation and maintenance shall be stored there. 6.2 230/400V self-provided generator sets 6.2.1 The generator sets, as well as the control, power distribution, and maintenance rooms, can be installed separately ； They can be installed together provided that the electrical safety distances are maintained and the fire protection requirements are satisfied. 6.2.2 The exhaust duct of the generator set must extend outside. Fire extinguishers capable of putting out electrical fires must be installed in the generator set and its control and power distribution rooms; storage tanks for oil are strictly prohibited. 6.2.3 The power supply of the generator set must be interlocked with the external power line supply; parallel operation is strictly prohibited. 6.2.4 The generator set shall adopt a three-phase four-wire power supply system with the power source neutral point directly grounded, along with an independent TN-S neutral grounding protection system; the value of its working ground resistance shall meet the requirements specified in Article 5.3.1 of these specifications. 6.2.5 The generator control panel should be equipped with the following instruments: 1 AC voltage meter ； 2 AC ammeter ； 3 Active power meter ； 4 Electricity meter ； 5 Power Factor Table ； 6 Frequency Table ； 7 DC ammeter. 6.2.6 The generator power supply system shall be equipped with a power isolation switch as well as protective devices against short circuits, overloads, and electric leakage. When the power isolation switch is opened, there should be a clearly visible break point. 6.2.7 When generator sets are operated in parallel, a synchronization device must be installed, and power shall be supplied to the load only after the sets are synchronized. 7 Distribution Lines 7.1 Overhead Lines 7.1.1 Insulated wires must be used for overhead lines. 7.1.2 Overhead lines must be installed on dedicated utility poles; it is strictly prohibited to install them on trees, scaffolding, or other structures. 7.1.3 The selection of the cross-sectional area of overhead line conductors shall meet the following requirements: 1 The calculated load current in the conductor shall not exceed its allowable current capacity for continuous long-term operation. The voltage deviation at the end of the 2-wire circuit shall not exceed 5% of its rated voltage. 3 The cross-sectional area of the N and PE wires in three-phase four-wire systems shall be not less than 50% of the cross-sectional area of the phase wires, while the cross-sectional area of the neutral wire in single-phase systems is the same as that of the phase wire. 4 According to the mechanical strength requirements, the cross-sectional area of insulated copper wires shall be no less than 10 mm2, and that of insulated aluminum wires shall be no less than 16 mm2. 5 Within the span across railways, highways, rivers, and power lines, the cross-sectional area of the insulated copper wire shall be no less than 16 mm2. The cross-sectional area of the insulated aluminum wire shall be not less than 25 mm2. 7.1.4 Within one span of an overhead line, the number of joints per layer of conductors shall not exceed 50% of the number of conductors in that layer, and a single conductor shall have only one joint. There shall be no joints in the overhead lines within the span of railways, highways, rivers, and power lines. 7.1.5 The phase sequence of overhead lines shall comply with the following provisions: 1 When power and lighting lines are installed on the same crossarm, the phase sequence of the conductors is as follows: starting from the left side facing the load, they are L1, N, L2, L3, PE ； 2 When the power and lighting cables are installed separately on the upper crossarm at the second floor, the sequence of the wire phases is as follows: starting from the left side facing the load, on the upper crossarm, they are L1, L2, L3 ； On the lower crossarm, facing the load, they are L1 (L2, L3), N, and PE in sequence from the left. 7.1.6 The span of overhead lines shall not exceed 35 m. 7.1.7 The spacing between conductors of overhead lines shall not be less than 0.3 m, and the spacing between the two conductors near the pole shall not be less than 0.5 m. 7.1.8 The minimum vertical distance between the crossarms of overhead lines shall not be less than the values specified in Table 7.1.8-1 ； The crossarm should be made of angle steel or square timber; for low-voltage iron crossarms, angle steel should be selected in accordance with Table 7.1.8-2, while the cross-sectional dimensions of square timber crossarms should be 80mm×80mm ； The length of the crossarm shall be selected according to Table 7.1.8-3. Table 7.1.8-1 Minimum vertical distance between crossarms (m) Table 7.1.8-2 Selection of angle steel for low-voltage iron crossarms Table 7.1.8-3 Selection of crossarm length 7.1.9 The distance between overhead lines and adjacent lines or fixed objects shall comply with the provisions in Table 7.1.9. 7.1.10 For idle lines, reinforced concrete poles or wooden poles are preferred. Reinforced concrete poles must not have exposed rebar, cracks wider than 0.4 mm, or twisting ； The wooden pole must not be rotten, and its diameter at the top should not be less than 140 mm. Table 7.1.9 Distance between overhead lines and adjacent lines or fixed objects 7.1.11 The burial depth of utility poles should be 1/10 of the pole’s length plus 0.6 m; the backfill soil should be compacted in layers. In soft soil, it is advisable to increase the burial depth or use clamps and other means for reinforcement. 7.1.12 For straight poles and poles with angles of 15° or less, a single crossarm with a single insulator may be used; however, when crossing vehicle lanes, a single crossarm with two insulators should be employed ； For angle rods between 15° and 45°, double cross-arms with double insulators should be used ； For corner poles at an angle of 45° or more, cross arms should be used. 7.1.13 Insulators for overhead lines shall be selected in accordance with the following principles: 1. Pin-type insulators shall be used for straight poles ； 2. The tension poles use butterfly insulators. 7.1.14 The guy wires for utility poles should consist of no fewer than 3 strands of galvanized steel wire with a diameter of D4.0mm. The angle between the tie rod and the electric pole should be between 30° and 45°. The burial depth of the tie wire shall not be less than 1m. If the pole tie passes between the conductors, a tie insulator should be installed at a height of 2.5 m above the ground. 7.1.15 When it is not possible to install guy wires due to constraints imposed by the surface conditions, struts can be used as a substitute for guy wires. The burial depth of these struts must be at least 0.8 m, and their bases should be supported by a base plate or stones. The angle between the strut and the electric pole should be 30°. 7.1.16 The service conductor shall have no joints within the span, and the height of the incoming conductor above the ground shall not be less than 2.5 m. The minimum cross-sectional area of the service drop cable shall comply with the requirements specified in Table 7.1.16-1. The distance between the conductors of the power receiving line and between them and adjacent lines shall meet the requirements of Table 7.1.16-2. Table 7.1.16-1 Minimum cross-section of service conductors Table 7.1.16-2 Spacing between service conductors and adjacent lines 7.1.17 Overhead lines must be equipped with short-circuit protection. When fuses are used for short-circuit protection, the rated current of their fusing elements should not exceed 1.5 times the allowable current-carrying capacity of exposed insulated wires under continuous long-term loading. When a circuit breaker is used for short-circuit protection, the setting value of its instantaneous overcurrent trip device should be less than the single-phase short-circuit current at the end of the circuit. 7.1.18 Overload protection must be provided for overhead lines. When fuses or circuit breakers are used for overload protection, the allowable current-carrying capacity of insulated wires under continuous long-term loading should not be less than 1.25 times the rated current of the fuse element or the setting value of the long-time delay overcurrent trip device of the circuit breaker. 7.2 Cable Lines 7.2.1 The cable must contain all the working conductors as well as the conductors used as protective neutral or protective wires. Cable lines that require three-phase four-wire power distribution must use five-core cables. A five-core cable must include insulating conductors in light blue and green/yellow. The light blue core wire must be used as the N wire ； Green/yellow dual-color core wires must be used as PE wires; mixing them is strictly prohibited. 7.2.2 The selection of the cable cross-section shall comply with the provisions of paragraphs 1, 2, and 3 of Article 7.1.3 of these specifications, and shall be determined based on its allowable current-carrying capacity under long-term continuous loading and the allowable voltage deviation. 7.2.3 Cable lines shall be laid underground or overhead; it is strictly prohibited to lay them exposed on the ground, and mechanical damage as well as medium corrosion shall be avoided. Orientation markers should be provided for buried cable routes. 7.2.4 The cable type should be selected based on the installation method and environmental conditions. Armored cables are recommended for underground installation ； When using unarmored cables, they should be waterproof and resistant to corrosion. Unarmored cables are preferred for overhead installation. 7.2.5 The depth at which cables are buried directly in the ground should not be less than 0.7 m. Fine sand with a thickness of not less than 50 mm should be spread evenly around the cables on their upper, lower, left, and right sides, after which a hard protective layer such as bricks or concrete slabs should be applied. 7.2.6 For buried cables passing through buildings, structures, roads, areas prone to mechanical damage, and sports venues, as well as from a height of 2.0 m above the ground to a depth of 0.2 m underground, protective sleeves must be installed; the inner diameter of these protective sleeves shall be no less than 1.5 times the outer diameter of the cable. 7.2.7 The parallel distance between buried cables and external electrical cables as well as ducts in their vicinity shall not be less than 2 m, while the crossing distance shall not be less than 1 m. 7.2.8 The joints of buried cables shall be located in junction boxes on the ground; these junction boxes must be waterproof, dustproof, and protected from mechanical damage, and they should be placed away from areas that are prone to fire, explosion, or corrosion. 7.2.9 Aerial cables shall be laid along utility poles, supports, or walls and secured using insulators. The binding wires must be insulated, and the spacing between fixing points shall be such that the cable can withstand the load resulting from its own weight. The laying height shall comply with the requirements for the laying height of aerial lines specified in Section 7.1 of these specifications; however, when laid along a wall, the maximum sag distance from the ground shall not be less than 2.0 m. Aerial cables must never be laid along scaffolding, trees, or other structures. 7.2.10 Cable lines within under-construction projects must be introduced by burying the cables underground; it is strictly prohibited to introduce them through scaffolding. When cables are installed vertically, vertical shafts and vertical tunnels in the construction site should be made full use of, and the installation should be carried out as close as possible to the center of electrical load; there must be at least one fixing point per floor. When cables are laid horizontally, they should be firmly fixed along walls or doorways, with the maximum sag distance from the ground not being less than 2.0 m. For decoration and renovation projects or other special phases, a separate construction power usage plan should be prepared. The power cable can be laid along wall corners or the floor, but measures must be taken to protect it from mechanical damage and electrical hazards. 7.2.11 Cable circuits must be equipped with short-circuit protection and overload protection. The selection of these protective devices and cables shall comply with the requirements of Articles 7.1.17 and 7.1.18 of this specification. 7.3 Indoor Wiring 7.3.1 Indoor wiring must use insulated wires or cables. 7.3.2 Indoor wiring shall be installed using insulator posts, porcelain (plastic) clamps, insulated grooves, conduits, or steel cables, depending on the type of wiring. In humid areas or when installed underground, non-cable wiring must be laid within pipes, and the pipe ends and joints must be sealed ； When metal pipes are used for installation, they must be equipotentially connected and must also be connected to the PE wire. 7.3.3 The height of indoor exposed main cables that are not buried above the ground shall not be less than 2.5 m. 7.3.4 The outdoor end of the overhead service entrance wire shall be fixed using insulators; it shall be protected by pipes where it passes through walls, shall be at a height of not less than 2.5 m above the ground, and rain protection measures shall be taken. 7.3.5 The cross-sectional area of the wires or cables used for indoor wiring shall be determined based on the calculated load of the electrical equipment or circuits; however, the cross-sectional area of copper wires shall not be less than 1.5 mm2, and that of aluminum wires shall not be less than 2.5 mm2. 7.3.6 The spacing between hangers for cable wiring should not exceed 12 m. When using ceramic clamps to secure wires, the distance between wires should not be less than 35 mm, and the distance between ceramic clamps should not be greater than 800 mm ； When using porcelain insulators to fix wires, the distance between wires should not be less than 100 mm, and the distance between porcelain insulators should not exceed 1.5 m ； When using sheathed insulated wires or cables, they can be directly laid on steel cables. 7.3.7 Indoor wiring must be equipped with short-circuit protection and overload protection. The selection of devices for short-circuit and overload protection, as well as the insulated wires and cables, shall comply with the requirements of Articles 7.1.17 and 7.1.18 of this specification. For insulated conductor circuits laid in conduits, the rated current of the fuse used for short-circuit protection shall not be greater than 2.5 times the allowable current-carrying capacity of the insulated conductors under long-term continuous loading. 8 Distribution Boxes and Switch Boxes 8.1 Installation of Distribution Boxes and Switch Boxes 8.1.1 The distribution system should be equipped with distribution cabinets or main distribution boxes, sub-distribution boxes, and switch boxes, to implement a three-level distribution system. The power distribution system should ensure balanced three-phase loads. Single-phase electrical equipment rated at 220V or 380V should be connected to a 220/380V three-phase four-wire system ； When the current in a single-phase lighting circuit exceeds 30A, it is advisable to use a 220/380V three-phase four-wire power supply. The installation of indoor distribution cabinets shall comply with the provisions of Section 6.1 of these specifications. 8.1.2 Several distribution panels can be installed below the main power distribution panel ； Several switch boxes can be installed below the distribution box. The main power distribution box should be located in an area close to the power source, while the sub-distribution boxes should be placed in areas where electrical equipment or loads are concentrated. The distance between a sub-distribution box and a switch box should not exceed 30 meters, and the horizontal distance between a switch box and the fixed electrical equipment it controls should not exceed 3 meters. 8.1.3 Each electrical device must have its own dedicated switch box; it is strictly prohibited to use the same switch box to control 2 or more electrical devices (including sockets). 8.1.4 The power distribution box and the lighting distribution box should be installed separately. When the merging is set to the same distribution box, power and lighting should be supplied via separate circuits ； The power switch box and the lighting switch box must be located separately. 8.1.5 Distribution boxes and switch boxes shall be installed in dry, well-ventilated areas at normal temperatures; they must not be placed in environments with harmful gases, smoke, moisture, or other hazardous substances that could cause damage to them. Nor should they be located in areas prone to impact from external solid objects, severe vibrations, liquid splashes, or exposure to heat sources. Otherwise, it should be removed or protected. 8.1.6 There should be sufficient space and passages around the distribution box and switch box for two people to work simultaneously; no items that may hinder operation or maintenance shall be stored there, nor shall there be any bushes or weeds. 8.1.7 Distribution boxes and switch boxes shall be made of cold-rolled steel plates or flame-retardant insulating materials. The thickness of the steel plates should be between 1.2 and 2.0 mm; the thickness of the steel plates used for switch boxes must not be less than 1.2 mm, while that of the plates used for distribution boxes must not be less than 1.5 mm. The surface of these boxes shall be treated to prevent corrosion. 8.1.8 Distribution boxes and switch boxes shall be installed properly and firmly. The vertical distance from the center of fixed distribution boxes and switch boxes to the ground should be 1.4 to 1.6 meters. Mobile distribution boxes and switch boxes should be installed on sturdy and stable supports. The vertical distance from its center point to the ground should be 0.8–1.6 m. 8.1.9 Electrical appliances (including sockets) inside distribution boxes and switch boxes should first be installed on metal or non-wooden flame-retardant insulating mounting plates, before being securely fastened as a whole inside the distribution box or switch box. The metal electrical mounting plate and the metal enclosure should be electrically connected. 8.1.10 The electrical appliances (including sockets) in the distribution boxes and switch boxes shall be fixed to the electrical installation panels at their designated positions, and must not be tilted or loose. 8.1.11 The electrical installation panel of the distribution box must be equipped with separate terminals for the N wire and the PE wire. The N-terminal block must be insulated from the metal electrical mounting plate ； The PE wire terminal block must be electrically connected to the metal electrical mounting plate. The N wire in the incoming and outgoing lines must be connected through the N wire terminal block ； The PE wire must be connected through the PE wire terminal block. 8.1.12 The connection wires inside distribution boxes and switch boxes must be insulated copper wires. The color markings for wire insulation shall be arranged in an orderly manner in accordance with the requirements of Clause 5.1.11 of these specifications ； Wire branch connections shall not be made by bolt compression; instead, welding should be used along with insulating wrapping, ensuring that no exposed live parts are present. 8.1.13 The metal enclosures of distribution boxes and switch boxes, the metal electrical installation panels, as well as the metal bases and housings of electrical devices when they are not under voltage must be electrically connected to the PE wire through PE wire terminal plates. The metal doors of these boxes must be electrically connected to the metal enclosures using braided soft copper wire. 8.1.14 The dimensions of the distribution boxes and switch boxes should be appropriate to the number and size of the electrical appliances contained within them. The installation dimensions for the electrical appliances on the installation panels inside these boxes can be determined according to Table 8.1.14. 8.1.15 The inlet and outlet ports for wires in distribution boxes and switch boxes shall be located on the bottom surface of the box. Table 8.1.14 Selected values for electrical appliance installation dimensions in distribution boxes and switch boxes. 8.1.16 Fixed wire clamps shall be installed at the inlet and outlet ports of distribution boxes and switch boxes; the wires entering and leaving these boxes shall be fitted with insulating sleeves and bundled together before being secured to the box, so as to avoid direct contact with the box itself. The incoming and outgoing wires of mobile distribution boxes and switch boxes shall use rubber-sheathed insulated cables, with no joints allowed. 8.1.17 The exterior structure of distribution boxes and switch boxes shall be capable of protecting against rain and dust. 8.2 Selection of electrical equipment 8.2.1 The electrical devices in distribution boxes and switch boxes must be reliable and in good condition; it is strictly prohibited to use damaged or substandard electrical equipment. 8.2.2 The electrical equipment in the main distribution panel shall have power isolation capabilities, as well as functions for normally connecting and disconnecting circuits, and for protecting against short circuits, overloads, and electric leakage. The electrical installations should comply with the following principles: 1 When a main leakage protector is installed on the main circuit, a main isolating switch and branch isolating switches, as well as main circuit breakers or branch circuit breakers, and main fuses or branch fuses, should also be installed. When the main leakage protector installed is a circuit breaker that provides protection against short circuits, overloads, and leakage, it may not be necessary to have a main circuit breaker or main fuse. 2 When branch circuit leakage protectors are installed for each branch circuit, a main isolating switch and branch circuit isolating switches, as well as a main circuit breaker and branch circuit breakers, or main fuses and branch circuit fuses, should also be installed. When the leakage protector installed at the branch circuit is a leakage circuit breaker that also has functions for short-circuit, overload, and leakage protection, it may be unnecessary to install a branch circuit breaker or a branch circuit fuse. 3 The isolation switch should be installed at the power supply inlet, and it should be an isolation device that provides a visible disconnection point when switched off, and is capable of disconnecting all poles of the power supply simultaneously. If circuit breakers with visible breaking points are used, there is no need to install a separate isolating switch. 4 Fuses should be products with reliable arc extinguishing and breaking capabilities. 5 The ratings and operating settings of the main switchgear should be compatible with those of the branch switchgear. 8.2.3 The main distribution panel shall be equipped with voltage meters, main current meters, wattmeters, and other necessary instruments. The installation of dedicated electric energy metering instruments shall comply with the requirements of the local power supply and consumption management authorities. When installing a current transformer, its secondary circuit must have a connection point with the protective neutral wire, and it is strictly prohibited to disconnect the circuit. 8.2.4 The distribution box shall be equipped with a main isolating switch and branch isolating switches, as well as a main circuit breaker and branch circuit breakers, or a main fuse and branch fuses. Its setting and selection shall meet the requirements of Article 8.2.2 of these specifications. 8.2.5 The switch box must be equipped with a disconnector, circuit breaker or fuse, as well as a leakage protector. When the leakage protector is a leakage circuit breaker that also has functions for short-circuit and overload protection, it is not necessary to install a circuit breaker or fuse. The isolating switch should be an isolating device that provides a visible disconnection point when switched off, capable of disconnecting all poles of the power supply, and it should be installed at the power inlet side. When the circuit breaker has a visible breaking point, it is not necessary to provide a separate isolating switch. 8.2.6 The isolating switch in the switch box can only be used to directly control lighting circuits and power circuits with a capacity of no more than 3.0 kW, but it should not be operated frequently. Power circuits with a capacity greater than 3.0 kW should be controlled by circuit breakers; when operated frequently, contactors or other starting control devices should also be installed. 8.2.7 The rated values and operating setting values of various switching devices in the switchgear box shall be compatible with the rated values and characteristics of the electrical equipment they control. The specifications of the electrical equipment in the general motor switch box can be selected according to Appendix C of this specification. 8.2.8 The leakage protector shall be installed on the side of the main distribution box or switch box that is closest to the load, and shall not be used to start electrical equipment. 8.2.9 The selection of residual current devices shall comply with the provisions of the current **standards: ‘General Requirements for Residual Current Devices’ GB 6829 and ‘Requirements for the Installation and Operation of Residual Current Devices’ GB 13955. 8.2.10 The rated leakage operating current of the leakage protector in the switch box shall not be greater than 30mA, and the rated leakage operating time shall not be greater than 0.1s. Leakage protectors used in humid or corrosive environments should be splash-proof types, with a rated leakage operating current not exceeding 15mA and a rated leakage operating time not exceeding 0.1s. 8.2.11 The rated leakage operating current of the leakage protector in the main distribution panel shall be greater than 30 mA, and the rated leakage operating time shall be greater than 0.1 s; however, the product of its rated leakage operating current and rated leakage operating time shall not be greater than 30 mA•s. 8.2.12 The number of poles and wires of the leakage protectors in the main distribution box and switch boxes must match the number of phases and wires of the loads on their load side. 8.2.13 For leakage protectors in distribution boxes and switch boxes, it is advisable to use products without an auxiliary power supply (electromagnetic type), or products with an auxiliary power supply that can automatically disconnect in the event of a failure of that supply (electronic type). When using auxiliary power supply-type (electronic) products that cannot be automatically disconnected in the event of a failure of the auxiliary power supply, phase loss protection should also be installed. 8.2.14 The residual current device shall be installed and used in accordance with the product instructions. For residual current devices that have been out of use for a long time and are now being reused or used continuously, their characteristics should be checked on a monthly basis; any issues found should be repaired or the devices replaced promptly. The correct wiring method for using a residual current device should be selected according to Figure 8.2.14. 8.2.15 Plugs and sockets shall not be used for movable connections at the power inlet ends of distribution boxes and switch boxes. Figure 8.2.14 Schematic of the wiring method for using a leakage protector L1, L2, L3 – phase wires ； N – Working neutral wire ； PE – Keep the neutral wire and protective wire ； 1 – Working ground ； 2 – Repeated grounding ； T – Transformer ； RCD – Leakage protector ； H – Lighter ； W – Welding machine ； M – Motor 8.3 Use and Maintenance 8.3.1 The distribution boxes and switch boxes should have names, purposes, circuit identification markings, and system wiring diagrams. 8.3.2 The doors of distribution boxes and switch boxes shall be locked and kept under the responsibility of a designated person. 8.3.3 Distribution boxes and switch boxes should be inspected and maintained regularly. Inspection and maintenance personnel must be professional electricians. During inspection and maintenance, insulating shoes and gloves must be worn as required, electrical insulating tools must be used, and records of the inspection and maintenance work must be kept. 8.3.4 When performing regular maintenance and inspections on distribution boxes and switch boxes, it is necessary to disconnect the corresponding power isolation switch at the upstream level to cut off the power, and hang a sign reading “Do not close – work in progress” to indicate that the power is off; working on these devices while they are still powered is strictly prohibited. 8.3.5 The distribution boxes and switch boxes must be operated in the following sequence: 1. The sequence for supplying power is: main distribution box → sub-distribution box → switch box ； 2 The sequence for power outage operations is: switch box → distribution box → main power distribution box. However, emergency situations involving electrical failures are an exception. 8.3.6 When work at the construction site is suspended for more than 1 hour, the power switch box should be powered off and locked. 8.3.7 The operators of the switchgear box must meet the requirements specified in Article 3.2.3 of these specifications. 8.3.8 No miscellaneous items shall be placed inside the distribution boxes or switch boxes, and they must be kept clean. 8.3.9 No other electrical equipment shall be arbitrarily connected inside the distribution box or switch box. 8.3.10 The electrical equipment and wiring inside distribution boxes and switch boxes must not be altered arbitrarily. When replacing the fuse element, it is strictly prohibited to use an element that does not meet the original specifications. Before use each day, the leakage protector should be tested by pressing the leakage test button once; it must not be used if the test does not proceed normally. 8.3.11 The incoming and outgoing wires of distribution boxes and switch boxes must not be subjected to external forces, and must not come into contact with sharp metal edges, highly corrosive substances, or flammable and explosive materials. 9 Electric construction machinery and hand-held electric tools 9.1 General provisions 9.1.1 The selection, use, inspection, and maintenance of electric construction machinery and hand-held electric tools at construction sites shall comply with the following provisions: 1 The selected electric construction machinery, hand-held electric tools, and their electrical safety devices must meet the requirements of the relevant **current mandatory standards, and they must come with a product certificate and user manual ； 2 Establish and implement a system assigning dedicated personnel and aircraft, along with regular inspections and maintenance ； 3 The grounding shall meet the requirements of Articles 5.1.1 and 5.1.2 of these specifications; there shall be no less than 2 connection points between the metal base and housing of equipment that generates vibration during operation and the PE wire ； 4 The leakage protection meets the requirements of Articles 8.2.5, 8.2.8–8.2.10, as well as Articles 8.2.12 and 8.2.13 of these specifications ； 5 Use, inspect, and maintain in accordance with the instruction manual. 9.1.2 Tower cranes, external elevators, metal operating platforms for slipform templates, and material hoists that require lightning protection devices shall be provided with repeated grounding in addition to being connected to the PE wire. Electrical connection must be ensured between the metal structural components of the equipment. 9.1.3 Plastic enclosures in hand-held electric tools: Class II tools and Class III tools used in hand-held electric tools in general areas do not require a PE wire. 9.1.4 For the supply cables of electric construction machinery and hand-held electric tools, jointless rubber-sheathed copper-core flexible cables should be used based on their calculated load; such cables must meet the requirements specified in Part 1 (General Requirements) and Part 4 (Flexible Wires and Cables) of the current standard **“Rubber-Insulated Cables with a Rated Voltage of 450/750V and Below” GB 5013 ； Its cross-section can be selected according to Appendix C of this specification. The number of core wires in the cable should be determined based on the load, as well as the number of phases and wires in the control equipment; for a three-phase four-wire system, a five-core cable should be used ； For three-phase three-wire systems, a four-core cable should be used ； When single-phase electrical appliances are used in three-phase electrical equipment, a five-core cable should be selected ； For single-phase two-wire systems, a three-core cable should be used. The cable conductors shall comply with the provisions of Clause 7.2.1 of this specification, wherein the PE conductor shall be a green/yellow dual-color insulated wire. 9.1.5 In the switch box of each electric construction machine or hand-held electric tool, in addition to overload, short-circuit, and leakage protection devices, an isolating switch or a circuit breaker with a visible breaking point shall be installed as required by Clause 8.2.5 of this code, and control devices shall be installed as required by Clause 8.2.6 of this code. The control electrical devices in the forward and reverse operation control apparatus shall be automatic control devices such as contactors and relays; manual two-way changeover switches shall not be used as control electrical devices. Electrical specifications can be selected according to Appendix C of this specification. 9.2 Lifting Machinery 9.2.1 The electrical equipment of tower cranes shall meet the requirements specified in the current **standard, the ‘Safety Regulations for Tower Cranes’ GB 5144. 9.2.2 Tower cranes shall be provided with repeated grounding and lightning protection grounding in accordance with the requirements of Article 5.4.7 of these specifications. The installation of the grounding devices for track-mounted tower cranes shall meet the following requirements: 1. A set of grounding devices shall be installed at each end of the track ； Make an electrical connection at the joint of the two tracks, and provide a circular electrical connection at the ends of both tracks ； 3 A set of grounding devices shall be installed every 30 m or less along the longer track. 9.2.3 The safety distance between tower cranes and external power lines shall meet the requirements of Article 4.1.4 of these specifications. 9.2.4 The cables of track-mounted tower cranes must not be dragged along the ground. 9.2.5 Tower cranes that require night operation shall be equipped with floodlights facing the working area. 9.2.6 For tower cranes with a tower height of more than 30 m, red signal lights shall be installed at the top of the tower and at the end of the boom. 9.2.7 Tower cranes operating near strong electromagnetic wave sources require operators to wear insulated gloves and shoes. Insulating isolation measures should be taken between the hook and the crane body, or a temporary grounding device should be attached to the hook when lifting objects from the ground. 9.2.8 Emergency stop switches shall be installed both inside and outside the elevator car for outdoor use. 9.2.9 Limit switches shall be installed at the upper and lower limit positions of outdoor elevators and material hoists. 9.2.10 Before starting operation each day, external elevators and material lifters must undergo a no-load inspection of their travel switches, limit switches, emergency stop switches, drive mechanisms, and brakes; they may be used only after everything is functioning properly. Fall prevention measures must be in place during inspection. 9.3 Pile-driving machinery 9.3.1 The sealing performance of the motors for submersible drilling machines shall meet the requirements of IP68 as specified in the current standard \"Degrees of protection provided by enclosures (IP codes)\", GB 4208. 9.3.2 The load cable for the submersible motor shall be a flexible copper-core cable with a waterproof rubber sheath, with a length of not less than 1.5 m, and it must not be subjected to external forces. 9.3.3 The residual current device in the switch box of the submersible drilling machine must meet the requirements for residual current devices used in humid environments as specified in Article 8.2.10 of these specifications. 9.4 Earthmoving Machinery 9.4.1 The residual current devices in the switchboxes of earthmoving machinery must meet the requirements specified in Article 8.2.10 of these specifications regarding residual current devices to be used in humid environments. 9.4.2 The connection points for the PE wire of the compaction machinery shall be no less than 2. 9.4.3 The load line of the ramming machine shall use a weather-resistant rubber-sheathed copper-core flexible cable. 9.4.4 When using ramming machinery, insulating equipment must be worn as required, and a dedicated person should be assigned to adjust the cables during use; the length of the cables should not exceed 50 m. Cables must not be twisted, kinked, or crossed by earthmoving machinery. 9.4.5 When multiple ramming machines operate side by side, the distance between them shall not be less than 5 m ； When working in sequence, the distance between them must be no less than 10m. 9.4.6 The control handles of compaction machinery must be insulated. 9.5 Welding Machinery 9.5.1 Welding machinery should be placed in a location that is protected from rain, dry, and well-ventilated. Flammable and explosive materials are not allowed at the welding site. 9.5.2 The length of the primary side power cable of the AC arc welding machine transformer should not exceed 5 m, and a protective cover must be installed at the power inlet. The commutator of a generator-type DC welding machine should be regularly inspected and maintained to eliminate any abnormal electric sparks that may occur. 9.5.3 The leakage protectors in the switch box of welding machinery must meet the requirements of Article 8.2.10 of these specifications. AC welding machines should be equipped with secondary-side electric shock protection devices. 9.5.4 The secondary cable of welding machinery shall be a flexible copper-core cable with a waterproof rubber sheath; the length of the cable shall not exceed 30 m. Metal components or structural rebar shall not be used as a substitute for the ground wire of the secondary cable. 9.5.5 Protective equipment must be worn when using welding machinery for welding. Welding work in the open rain is strictly prohibited. 9.6 Handheld electric tools 9.6.1 In areas where the air humidity is below 75%, Class I or Class II handheld electric tools can be used; there must be no less than 2 connection points between the metal casing and the PE wire ； Except for plastic-encased Class II tools, the rated leakage operating current of the residual current device in the relevant switch box should not exceed 15 mA, and the rated leakage operating time should not exceed 0.1 s; the plug of its load cable should be equipped with dedicated protective contacts. The sockets and plugs used should be structurally consistent to prevent the mixing of conductive contacts and protective contacts. 9.6.2 When operating in humid areas and on metal frameworks, Class II or Class III hand-held power tools powered by a safety isolation transformer must be used. When using metal-clad Class II hand-held power tools, they must meet the requirements of Clause 9.6.1 of these specifications ； Their switch boxes and control boxes should be located outside the work area; the use of Class I handheld electric tools is strictly prohibited in humid areas or on metal frameworks. 9.6.3 In confined spaces, Class III handheld electric tools powered by safety isolation transformers must be used; both their switch boxes and the safety isolation transformers should be located outside the confined space, and a PE wire must be connected. The selection of residual current devices shall comply with the requirements for such devices in humid or corrosive environments as specified in Article 8.2.10 of these specifications. Someone should be monitoring from outside during the operation. 9.6.4 The load cable for hand-held power tools shall be a weather-resistant rubber-sheathed copper-core flexible cable, and must not have any joints. 9.6.5 The casing, handle, plug, switch, load cable, etc. of handheld power tools must be in good condition. Insulation checks and no-load tests must be carried out before use; the tools can only be used once the insulation meets the requirements and they operate properly under no-load conditions. The insulation resistance shall not be less than the value specified in Table 9.6.5. Table 9.6.5 Insulation resistance limits for hand-held power tools Note: Insulation resistance is measured using a 500V megohmmeter. 9.6.6 When using hand-held power tools, insulating protective equipment must be worn as required. 9.7 Other electric construction machinery 9.7.1 The leakage protection for equipment such as concrete mixers, insert vibrators, plate vibrators, floor finishers, terrazzo machines, steel bar processing machinery, woodworking machinery, shield machines, and water pumps shall meet the requirements of Article 8.2.10 of these specifications. 9.7.2 The power cables for concrete mixers, insertion vibrators, plate vibrators, floor finishers, terrazzo machines, steel bar processing machinery, woodworking machinery, and shield tunneling machinery must be weather-resistant flexible cables with copper cores, and must be free of any damage or joints. The load cable for the water pump must be a flexible copper-core cable with a waterproof rubber sheath; it must not have any damage or connections, and it must not be subjected to any external forces. The load line of the shield machine must be firmly fixed, with a height from the ground of not less than 2.5 m. 9.7.3 When cleaning, inspecting, or repairing equipment such as concrete mixers, steel bar processing machinery, woodworking machinery, and shield tunneling machines, it is necessary to first disconnect the power supply at their switch boxes, ensure that there is a visible point where the power is cut off, and then close and lock the doors. 10 Lighting 10.1 General Provisions 10.1.1 In pits, holes, wells, during night work, or in areas such as factories, roads, warehouses, offices, canteens, dormitories, material storage areas, and places with poor natural lighting, general lighting, local lighting, or a combination of both should be provided. In a workplace, local lighting alone shall not be provided. At construction sites where operators need to evacuate promptly in the event of a power outage, emergency lighting equipped with a backup power source must be installed. 10.1.2 Field lighting should use lighting sources with high luminous efficiency and long lifespan. For areas that require extensive lighting, high-pressure mercury lamps, high-pressure sodium lamps, or halogen-tungsten lamps for mixed lighting should be used. 10.1.3 The selection of lighting fixtures must be determined based on the following environmental conditions: 1 In areas with normal humidity, open-type lighting fixtures should be used ； 2 In humid or highly humid areas, use sealed waterproof lighting fixtures or open-type lighting fixtures equipped with waterproof lamp holders ； 3 In areas with a high amount of dust but no risk of explosion or fire, use dust-proof lighting fixtures ； 4 In areas with explosion and fire hazards, explosion-proof lighting fixtures should be used according to the hazard level of the area ； 5 In areas with strong vibrations, use vibration-resistant lighting fixtures ； 6 In areas with strongly corrosive substances such as acids and alkalis, use acid- and alkali-resistant lighting fixtures. 10.1.4 The quality of lighting fixtures and equipment shall comply with the provisions of **current relevant mandatory standards; fixtures and equipment with aged or damaged insulation shall not be used. 10.1.5 For underground large-scale construction sites without self-illumination, a separate lighting power consumption plan shall be prepared. 10.2 Lighting Power Supply 10.2.1 For general areas, lighting fixtures with a rated voltage of 220V are suitable. 10.2.2 Safety extra-low voltage lighting fixtures should be used in the following special locations: Lighting in tunnels, civil air defense facilities, areas with high temperatures, areas with conductive dust, relatively humid environments, or places where the height of the lighting fixtures above the ground is less than 2.5 meters; the supply voltage in such cases should not exceed 36V ； 2 For lighting in humid areas and locations where live electrical parts are easily accessible, the supply voltage must not exceed 24V ； 3 For lighting in particularly humid areas, on conductive floors, inside boilers, or metal containers, the supply voltage must not exceed 12V. 10.2.3 The use of row lights shall meet the following requirements: 1 The supply voltage shall not exceed 36V ； 2 The lamp body and handle should be sturdy, well-insulated, and resistant to heat and moisture ； 3 The lamp base is firmly attached to the lamp body, and the lamp base has no switch ； 4 The bulbs have a metal protective mesh on the outside ； 5 The metal mesh, reflector, and suspension hooks are fixed to the insulated parts of the lamp. 10.2.4 For small work areas far from power sources, road lighting, security lighting, or lighting systems with a rated voltage of 12–36V, the allowable voltage deviation is -10% to 5% of the rated voltage value ； For the remaining locations, the allowable voltage deviation is ±5% of the rated voltage value. 10.2.5 Lighting transformers must be double-winding safety isolation transformers; autotransformers are strictly prohibited. 10.2.6 The lighting system should ensure a balanced three-phase load; on each single-phase circuit, the number of lights and sockets should not exceed 25, and the load current should not exceed 15A. 10.2.7 The primary side power cable of the portable transformer shall be a flexible copper cable with rubber or plastic insulation, without any joints in between; its length should not exceed 3 m. The green/yellow dual-colored wire may only be used as a PE wire, and the power plug shall be equipped with protective contacts. 10.2.7 The cross-sectional area of the working neutral wire shall be selected in accordance with the following provisions: 1 In single-phase two-wire and two-phase two-wire circuits, the cross-sectional area of the neutral wire is the same as that of the phase wires ； 2 In three-phase four-wire systems, when the lighting fixtures are incandescent lamps, the cross-sectional area of the neutral wire shall be not less than 50% of that of the phase wires ； When the light source is a gas discharge lamp, the cross-sectional area of the neutral wire is selected based on the current of the phase with the maximum load ； 3 In a three-phase lighting circuit with phase-by-phase disconnection, the cross-sectional area of the neutral wire is the same as that of the phase wire carrying the maximum load. 10.2.9 The installation of indoor and outdoor lighting circuits shall comply with the requirements of Chapter 7 of these specifications. 10.3 Lighting fixtures 10.3.1 The metal enclosures of lighting fixtures must be connected to the PE wire. The lighting switch box must be equipped with a disconnect switch, devices for protecting against short circuits and overloads, as well as a leakage protector; these requirements shall comply with Articles 8.2.5 and 8.2.6 of these specifications. 10.3.2 Outdoor 220V lighting fixtures must be installed at a height of no less than 3m above the ground, while indoor 220V lighting fixtures must be installed at a height of no less than 2.5m above the ground. The distance between ordinary lighting fixtures and flammable materials should not be less than 300 mm ； High-heat lighting devices such as spotlights and iodine-tungsten lamps should be kept at a distance of no less than 500 mm from flammable materials, and must not shine directly on them. When the required safety distance cannot be maintained, thermal insulation measures should be taken. 10.3.3 Each lamp post light should be equipped with a fuse for protection separately. The lamp holder cable should have waterproof bends. 10.3.4 Fluorescent tubes should be fixed using tube holders or suspended with suspension chains; the ballasts for fluorescent lamps must not be installed on flammable structures. 10.3.5 The installation height of iodine-tungsten lamps and metal halide lamps such as those using sodium, thallium, indium, etc., should be above 3 m. The lamp wires must be fixed to the terminals and must not be close to the surface of the lamp. 10.3.6 The base of the spotlight should be installed firmly, and the pivot should be tightened and fixed in the desired axis direction. 10.3.7 Screw-type lamp holders and their wiring shall meet the following requirements: 1. The insulated housing of the lamp holder must be free from damage and leakage ； The 2-phase wires are connected to the end attached to the center contact, while the neutral wire is connected to the end attached to the threaded port. 10.3.8 The wiring inside the lamp must be secure, while the wiring outside the lamp must be properly insulated and protected from moisture. 10.3.9 The lighting fixtures for temporary structures should be controlled by pull-cord switches, and the installation location of these switches should meet the following requirements: 1 The pull-cord switch should be located at a height of 2–3 meters above the ground, and at a horizontal distance of 0.15–0.2 meters from the entrance/exit; the end of the pull cord should point downward ； 2 The height of the other switches from the ground is 1.3 m, and their horizontal distance from the entrance/exit is 0.15～0.2 m. 10.3.10 The phase wire of the lamp must be controlled by a switch; the phase wire shall not be connected directly to the lamp. 10.3.11 For construction projects and mechanical equipment that affect the movement of aircraft or vehicles at night, conspicuous red signal lights must be installed. Their power supply should be located in front of the main power switch at the construction site, and an emergency backup power source should be provided in case the external power supply is disconnected. Appendix A: Average annual number of thunderstorm days nationwide Table A: Average annual number of thunderstorm days in major cities across the country Continued from Table A Continued from Table A Continued from Table A Continued from Table A Note: a denotes year, and d denotes day. Appendix B: Ball Rolling Method B.0.1 According to the ball rolling method, the protection area of a single lightning rod (based on the spark arrester) shall be determined as follows: 1 When the height of the lightning rod (h) is less than or equal to the ball rolling radius (hr) (Figure B.0.1-1), the protection radius of the lightning rod at the XX′ level corresponding to the height of the protected object, as well as its protection radius at ground level, can be calculated using the following formulas: Figure B.0.1-1 Protection area of a single lightning rod (h≤hr) Where h is the height of the lightning rod in meters ； hx——height of the protected object (m) ； rx —— protection radius at the XX′ plane at the height of the protected object (m) ； ro——Protection radius on the ground (m) ； hr——ball rolling radius (m). In the current **standard, the Code for Design of Lightning Protection of Buildings GB 50057, the rolling sphere radii for buildings classified as Category 1, 2, and 3 in terms of lightning protection are specified as 30m, 45m, and 60m respectively. For general construction sites in areas where the average annual number of thunderstorm days is greater than 15 days per year, tall structures and buildings with a height of 15 meters or more, as well as large construction machinery ； Or in areas where the average annual number of thunderstorm days is 15 days per year or less, tall structures and large construction machinery at a height of 20 meters or more can be treated in accordance with Category III lightning protection buildings. 2 When the height of the lightning rod (h) is greater than the rolling sphere radius (hr) (Figure B.0.1-2), the protection radius of the lightning rod at the XX′ level corresponding to the height of the structure being protected, as well as its protection radius at ground level, can be determined using the following formulas: B.0.2 According to the rolling sphere method, the protection area of a single lightning conductor (paratonnerre) should be determined in the following manner: When the height of the lightning conductor is greater than or equal to 2 times the rolling sphere radius, there is no protection area ； When the height of the lightning protection conductor is less than 2 times the rolling sphere radius (Figure B.0.2), the space between the arc formed by 2 times the rolling sphere radius (the cylindrical surface) and the ground constitutes the protection area. When hr＜h＜2hr, the height ho of the highest point within the protection area can be calculated using the following formula: When h≤hr, the height of the highest point within the protection area is equal to h: ho=h (B.0.2-2). The protection width bx of the lightning conductor at a height of hx in the XX′ plane can be calculated using the following formula: Figure B.0.1-2 shows the protection area covered by a single lightning rod (h＞hr), while Figure B.0.2 shows the protection area covered by a single overhead lightning conductor. The protection areas at both ends of the lightning conductor are determined using the method applicable to a single lightning rod. The protection areas covered by multiple lightning rods and multiple lightning conductors shall be determined in accordance with the current **standard, the Code for Design of Lightning Protection of Buildings GB 50057. Appendix C Motor Load Lines and Electrical Appliance Selection Table C Motor Load Lines and Electrical Appliance Selection Continued Table C Continued Table C Glossary of Terms Used in This Specification 1. To facilitate differentiated treatment when implementing the provisions of this specification, the terms with varying levels of strictness are defined as follows: 1) Indicates a very high level of strictness – it is mandatory to follow this requirement: The positive term used is “must”” ； The antonym uses “strictly prohibited”” ； 2) Indicates strictness – it should be done under normal circumstances: the positive term uses “should”” ； The negative form uses “should not” or “must not”” ； 3) Indicates that a slight choice is allowed, and that this should be done first when conditions permit: the positive term used is “it is appropriate”” ； The antonym uses “not suitable”” ； To indicate that there is a choice and that it is possible to do so under certain conditions, use “can”. Where the two provisions specify that execution should be in accordance with other relevant standards, it shall be expressed as “should be executed in accordance with...” or “should comply with...provisions (requirements)”. Technical Code for Safety of Temporary Electricity Use at Construction Sites JGJ46-2005 Explanations of the Provisions Preface The Technical Code for Safety of Temporary Electricity Use at Construction Sites, JGJ46-2005, was approved and issued by the Ministry of Construction via Announcement No. 322 on April 15, 2005. The leading institution for the first edition of this standard was Shenyang Institute of Building Engineering, with the China Academy of Building Research participating as well. To enable relevant personnel from design, construction, research, educational institutions, and other organizations to correctly understand and implement the provisions of these standards when using them, the drafting team of the \"Technical Code for Safety in Temporary Electricity Use at Construction Sites\" has prepared explanatory notes for each chapter, section, and article of these standards for reference by users in China. If you find any inaccuracies in the explanations provided for this provision during use, please send your comments to Shenyang Jianzhu University. Table of Contents 1 General Provisions 3 Temporary Power Supply Management 3.1 Organizational Design for Temporary Power Supply 3.2 Electricians and Personnel Using Electricity 3.3 Safety and Technical Documentation 4 Protection of External Power Lines and Electrical Equipment 4.1 Protection of External Power Lines 4.2 Protection of Electrical Equipment 5 Grounding and Lightning Protection 5.1 General Provisions 5.2 Protective Zero Connection 5.3 Grounding and Ground Resistance 5.4 Lightning Protection 6 Distribution Rooms and Self-Provided Power Sources 6.1 Distribution Rooms 6.2 230/400V Self-Provided Generator Sets 7 Distribution Lines 7.1 Overhead Lines 7.2 Cable Lines 7.3 Indoor Wiring 8 Distribution Boxes and Switch Boxes 8.1 Installation of Distribution Boxes and Switch Boxes 8.2 Selection of Electrical Devices 8.3 Use and Maintenance 9 Electric Construction Machinery and Handheld Electric Tools 9.1 General Provisions 9.2 Lifting Machinery 9.3 Piling Machinery 9.4 Earthmoving Machinery 9.5 Welding Machinery 9.6 Handheld Electric Tools 9.7 Other Electric Construction Machinery 10 Lighting 10.1 General Provisions 10.2 Lighting Power Supply 10.3 Lighting Devices 1 General Provisions 1.0.3 This clause comprehensively stipulates the three basic safety and technical principles that must be fully implemented in the electrical systems within the scope of application of these specifications. They serve as the main technical basis for ensuring safety in electrical installations at construction sites ； It is also a key technical measure to ensure electrical safety and prevent electric shock and electrical fire accidents. 3 Management of Temporary Electricity Use 3.1 Organizational Design for Temporary Electricity Use 3.1.1 The likelihood of electric shock and electrical fire accidents is related to the number, type, distribution of electrical equipment, as well as the calculated load. For construction sites where there is a large amount of electrical equipment (5 units or more) and the total capacity of such equipment is high (50 kW or more), in order to standardize the management of temporary electricity use, enhance electrical safety measures, and ensure safe electricity usage, this section provides guidelines for the organizational design of electrical systems based on the actual conditions at the construction site, in accordance with the current industry standard \"Safety Regulations for Electric Power Construction (Substation Section)\” DL 5009.3. These guidelines serve to guide the construction of electrical systems and ensure their safe and reliable operation. 3.1.2 This clause specifies the contents of the temporary power supply organization design, including the tasks that need to be completed, and is applicable universally. The basis for load calculation includes the capacity, type, grouping, and operating patterns of electrical equipment; the demand factor method can be employed ； Drawing the layout plan of the power distribution equipment is merely a requirement for installing distribution cabinets in rows within the power distribution room ； Both electrical safety measures and electrical fire prevention measures include technical and managerial aspects. 3.1.3 The temporary power supply organization design is a separate technical document. To ensure its role in guiding the safety of temporary power supply systems and electrical usage at the construction site, the relevant drawings must be prepared separately and shall not be combined with those from other types of construction organization designs. 3.1.4 and 3.1.5: To strengthen management and clarify responsibilities, these two clauses, in accordance with the current **standard \"Guidelines for Electrical Safety\" GB/T 13869 and the current industry standard \"Safety Procedures for Electric Power Construction (Substation Section)\" LD 5009.3, and taking into account the actual electrical usage conditions at construction sites, specify the procedures for preparing electrical organization designs and any changes to them, as well as the processes for reviewing and approving such designs. Among them, the relevant departments responsible for reviewing the temporary power supply organization design are the departments related to safety, technology, equipment, construction, materials, and supervision. 3.1.6 For smaller construction sites that meet the specified requirements, it may not be necessary to prepare an electrical utilization plan; however, safety measures for electrical use and electrical fire prevention measures must still be established. Just like in the case of temporary electrical utilization plans, the same procedures for preparation, review, and approval must be strictly followed. 3.2 Electricians and Persons Using Electricity 3.2.1 This clause is based on the provisions of the current **standard, the ‘Guidelines for Electrical Safety’ GB/T 13869, which prohibit persons who are not electricians from performing electrical work. 3.2.2 In accordance with the provisions of the current **standard ‘Guidelines for Electrical Safety’ GB/T 13869, and taking into account the characteristics of work at construction sites, this section sets out clear requirements regarding the electrical operation skills and protective skills of various personnel involved in electrical work, as well as matters related to education, training, and technical instructions. The persons using electricity as referred to in this article are those who directly operate electrical equipment for construction work. 3.2.3 This clause specifies that electricians and users of electrical equipment must work with valid certificates after receiving training. Electrical equipment refers to any facility or product used for power generation, transformation, transmission, distribution, or consumption, such as motors, transformers, electrical appliances, electrical measuring instruments, protective devices, wiring systems, and electrical tools. It also encompasses the mechanical assemblies or structural components associated with these devices, such as various electric machinery, power tools, lighting fixtures, welding machines, etc. Among them, electrical equipment that converts electrical energy into other forms of energy, such as motors, welders, lighting fixtures, electric machinery, and power tools, are also known as electrical load devices. 3.3 Safety Technology Documents 3.3.1 Among the 8 types of safety technology documents specified in this section, the test and inspection certificates for electrical equipment as well as the commissioning records shall be provided by the equipment manufacturer or by professional maintenance personnel. Articles 3.3.3 and 3.3.4 stipulate the inspection system for temporary electrical installations at construction sites and the procedures for carrying out such inspections. The maximum execution frequency is once a month at the construction site ； At the grassroots company, once per quarter. 4 Protection of Electrical Lines and Equipment 4.1 Protection of External Electrical Lines 4.1.1 This section sets out specific isolation protection measures to prevent direct electric shock to workers at construction sites, in accordance with the current **standard \"General Requirements for Devices and Equipment for Protection against Electric Shock\" GB/T 17054, as well as the International Electrotechnical Commission standard \"General Requirements for Devices and Equipment for Protection against Electric Shock\" IEC 1140:1992 regarding the principles of electrical isolation for protection. 4.1.2 The provisions in this clause are established in accordance with the principles regarding protection against direct contact set out in the current standard **\"Electrical Installations in Buildings – Protection Against Electric Shock\" GB 14821.1, as well as the current standard **\"Design Code for Overhead Power Lines of 66 kV and Below\" GB 50061 and the industry standard **\"Safety Work Procedures\" DL 409. Taking into account factors such as the erection of external scaffolding at construction sites and the activities of construction workers, these provisions specify the minimum safe operating distances necessary to prevent human beings from coming into direct contact with, or being in close proximity to, overhead power lines, either directly or indirectly through metal objects. The requirements set out in this provision are higher than those specified in the current industry standard, the \"Safety Regulations for Electric Power Work (Power Line Section)\». This is done, on the one hand, to ensure the safety of construction operations ； On the other hand, it provides space for installing protective facilities when the specified requirements are not met. 4.1.3 This clause is formulated in accordance with the current **standard \"Code for Design of Overhead Power Lines of 66 kV and Below\" GB 50061, and specifies the minimum safety distances to prevent direct or indirect contact with overhead power lines, taking into account factors such as vehicle transportation of materials at the construction site. 4.1.4 This clause is formulated in accordance with the current **standard \"Safety Regulations for Tower Cranes\" GB 5144 and the current industry standard \"Safety Work Regulations for Power Construction (High-Voltage Power Line Section)\" DL 5009.2. It sets out provisions to prevent cranes (including their booms and lifting ropes) as well as the items being lifted from coming too close to high-voltage power lines, and to prevent the dropped items from damaging such high-voltage power lines, taking into account factors such as the swinging motion of the items being lifted during crane operations. 4.1.6 The protective facilities specified in this clause comply with the current **standard \"Protection against electric shock in electrical installations of buildings\" GB 14821.1, as well as the corresponding International Electrotechnical Commission standard \"Safety requirements for electrical installations of buildings – Protection against electric shock\" IEC 364-4-41 (1992), regarding protective measures such as barriers, enclosures, and obstacles for preventing direct contact. Protective structures should be constructed using wood, bamboo, or other insulating materials, and should not be built from metal materials such as steel pipes. Warning signs on protective facilities must be clearly visible day and night. The minimum safe distance between protective facilities and external power lines is determined in accordance with the provisions set out in the current industry standard \"Safety Regulations for Power Construction (High-Voltage Power Line Section)\", DL 5009.2, regarding the minimum safe distance for work at heights and in proximity to live electrical conductors. Robust and stable protective facilities mean that they are capable of withstanding accidental impacts from falling people, tools, and equipment during construction, while maintaining their protective function. The IP31 rating specifies that the gaps in the protective enclosure prevent solid objects with a diameter of ø2.5mm from passing through. 4.1.7 This clause specifies further measures to be taken when the protection requirements of clause 4.1.6 cannot be met, emphasizing that construction must not proceed without any such measures in place. 4.2 Protection of electrical equipment 4.2.1 This section complies with the provisions of the current standards **“Guidelines for Electrical Safety” GB/T 13869, “Design Code for Electrical Installations in Explosive and Flammable Environments” GB 50058, and “Degrees of Protection Provided by Enclosures (IP Code)” GB 4208, and is suitable for the working conditions at construction sites. Regarding the protection of flammable and explosive materials, the specified protective measures and protection levels refer to the protective structures and measures for electrical equipment that are appropriate to the category of danger and the scope of the area ； For protection against pollution sources and corrosive agents, the specified protective measures and protection levels refer to the protective structures or measures that electrical equipment should have in environments already present with such pollution sources and corrosive agents, in order to be compatible with those environmental conditions. 4.2.2 This clause is formulated in light of the practice of installing electrical equipment outdoors at construction sites and of concurrent operations by different types of workers, aiming to prevent electrical accidents caused by mechanical damage to such equipment. 5 Grounding and Lightning Protection 5.1 General Provisions Articles 5.1.1 and 5.1.2, in accordance with the current standard \"Types of System Grounding and Safety Technical Requirements\" GB 14050 and taking into account the actual conditions at construction sites, specify the basic types of system grounding suitable for temporary electrical systems at such sites. They emphasize the use of the TN-S neutral protection system, prohibit the use of the TN-C system, and clearly define the methods for implementing the TN-S system in order to avoid the potential hazards associated with mixing TN and TT systems. The neutral point refers to the common connection point when a three-phase power supply is connected in a Y configuration. The neutral wire refers to the conductor that leads from the neutral point. The working neutral wire refers to the wire that extends from the neutral point when the neutral point is grounded, and serves as a power line, providing a path for power during operation. The protective neutral wire refers to a wire that is derived from the neutral point or the neutral line when the neutral point is grounded; it is not used as a power supply wire, but solely as a conductor for connecting the exposed conductive parts of electrical equipment. During operation, it serves only as a path for leakage current. 5.1.3 This clause is a supplementary provision to ensure that the TN-S system remains unaltered, and it is in compliance with the current **standard \"Types of System Grounding and Safety Technical Requirements\" GB 14050. 5.1.4 This clause is in compliance with the current **standard \"Types and Safety Technical Requirements for System Grounding\" GB 14050. 5.1.5 This clause is in line with the current **standard \"Technical Requirements for Isolation Transformers and Safety Isolation Transformers\" GB 13028, which is an equivalent adoption of the International Electrotechnical Commission standard \"Requirements for Isolation Transformers and Safety Isolation Transformers\" IEC 742 (1983), as well as the provisions of the current **standard \"Types of System Grounding and Their Safety Technical Requirements\" GB 14050. 5.1.6 This clause complies with the provisions of the current **standard, ‘Guidelines for Electrical Safety’ GB/T 13869. The phase wires are the three power lines that originate from the three separate power terminals of a three-phase power supply (generator or transformer) (denoted as L1, L2, L3 or A, B, C); they are also known as terminal wires and commonly referred to as live wires. 5.1.7 This clause is formulated in accordance with the current industry standard, the \"Code for Electrical Design of Civil Buildings\" JGJ/T 16, and ensures that the grounding resistance meets the required standards throughout the year. In Table 5.1.7, grounding electrodes with a burial depth greater than 2.5 m are referred to as “deeply buried grounding electrodes”. Clauses 5.1.8 and 5.1.9 are in compliance with the current standards **“Types and Safety Technical Requirements for System Grounding” GB14050, “Electrical Installations in Buildings – Part 5: Selection and Installation of Electrical Equipment, Chapter 54: Grounding Devices and Protective Conductors” GB 16895.3 (which is equivalent to the International Electrotechnical Commission standard IEC 364-5-54:1980), as well as the current industry standard **“Code for Electrical Design of Civil Buildings” JGJ/T 16. 5.1.10 This clause is in compliance with the current **standards \"Types and Safety Technical Requirements for System Grounding\" GB 14050, \"Design Code for Substations of 10 kV and Below\" GB 50053, the current **standard \"Color or Numerical Marking of Conductors\" GB 7947 (i.e., IEC standard IEC 446:1989), as well as the current **standard \"Code for Acceptance of Construction Quality of Building Electrical Engineering\" GB 50303. 5.2 Protective Zero Connection 5.2.1 This clause complies with the provisions regarding the zero connection protection of electrical equipment in the current standards **“Types and Safety Technical Requirements for System Grounding” GB 14050 and “Code for Construction and Acceptance of Grounding Systems in Electrical Installation Projects” GB 50169. 5.2.2 This clause is in accordance with the current **standard \"General requirements for protection against electric shock – Apparatus and equipment\" GB 17045 (which is equivalent to the International Electrotechnical Commission standard IEC 446:1992), as well as the current national standard \"Electrical installations in buildings – Protection against electric shock\" GB 14821.1, and the International Electrotechnical Commission standard \"Electrical installations in buildings – Protective measures against electric shock\" IEC 364-4-41:1992, which is adopted equivalently by this standard. 5.2.3 This clause is in compliance with the current **standard \"Code for Construction and Acceptance of Grounding Systems in Electrical Installation Projects\" GB 50169. 5.3 Grounding and Ground Resistance 5.3.1 This section complies with the current industry standard, the \"Code for Electrical Design of Civil Buildings\" JGJ/T 16. 5.3.2 This clause specifies the requirements for the grounding of the protective neutral wire in TN systems, in accordance with the principles set out in the current **standard \"Types and Safety Technical Requirements for System Grounding\" GB 14050. The regulations regarding the repeated grounding of the protective neutral wire in the TN system, as well as the value of the grounding resistance, are designed to reduce the voltage of the protective conductor with respect to ground in the event that the PE wire breaks at some point, and subsequently there is a short circuit or leakage current between the phase conductors of the electrical equipment and the protective conductor (or the exposed conductive parts of the equipment). This ensures that the protective devices installed in the system can cut off the power supply within a specified time frame. These requirements are expressed by the following two equations:
Zs•Ia ≤ U0
Zs•IΔn ≤ U0
Where Zs represents the impedance of the fault circuit (Ω) ； It—is the short-circuit setting current (A) of the short-circuit protection device ； IΔn ——Rated leakage operating current of the residual current device (A) ； U0——Power supply voltage of the faulty circuit (V). 5.3.3 This clause is another supplementary provision to ensure that the TN-S system remains unaltered. 5.3.4 This clause is formulated in accordance with the requirements of the current **standard \"Electrical Installations in Buildings – Part 5: Selection and Installation of Electrical Equipment, Chapter 54: Earthing Arrangements and Protective Conduits\" GB 16895.3 (which is equivalent to the International Electrotechnical Commission standard IEC 364-5-54:1980), as well as the current industry standard \"Code for Electrical Design of Civil Buildings\" JGJ/T 16. Among them, the minimum specified dimensions for materials used as artificial grounding electrodes are as follows: the thickness of angle steel plates must be no less than 4 mm, the wall thickness of steel pipes must be no less than 3.5 mm, and the diameter of round steel must be no less than 4 mm ； The reason why deformed steel bars are not allowed to be used is mainly that they have difficulty making close contact with the soil, resulting in unstable grounding resistance. Points 5.3.5 and 5.3.6 are in line with the current industry standard, the \"Code for Electrical Design of Civil Buildings\" JGJ/T 16, and take into account the fact that generators are primarily used as a power source to maintain supply when external power lines fail. 5.3.7 This clause is in line with the provisions on static electricity protection measures in the current **standard \"General Guidelines for Preventing Static Electricity Accidents\" GB 12158. 5.4 Lightning Protection 5.4.1 This clause is in line with the current industry standard, the \"Code for Electrical Design of Civil Buildings\" JGJ/T 16, which specifies measures to prevent lightning waves from penetrating distribution equipment via overhead lines in cases where no lightning arresters are used. Sections 5.4.2 to 5.4.5 comprehensively specify the installation and requirements for lightning protection devices at construction sites, in accordance with the current standards **\"Code for Design of Lightning Protection of Buildings\" GB 50057 and \"Safety Regulations for Tower Cranes\" GB 5144, taking into account the average annual number of thunderstorm days across different regions as well as the height of mechanical equipment at construction sites. The protection area of the lightning receptor in the lightning protection systems of adjacent buildings, structures, and other facilities refers to the protection area determined by the ball rolling method. The so-called rolling ball method involves selecting a spherical object with a radius hr, determined by the lightning protection category, and rolling it along the area that needs to be protected from direct lightning strikes. If the sphere comes into contact only with the lightning conductor (including metal objects used as lightning conductors), or only with the lightning conductor and the ground (including metal objects in contact with the earth and capable of withstanding lightning strikes), without touching the area that needs protection, then that part is protected by the lightning conductor. The protection area of a single lightning rod (lightning receptor) is shown in Figures B.0.1 and B.0.2; it consists of a symmetric cone formed by the areas between the arc curves MA′ and MB′ and the ground, as well as between the arc curves M′A′ and M′B′ and the ground. The power, control, lighting, signaling, and communication circuits of mechanical equipment are laid using steel pipes, and they are electrically connected to the metal structure of the equipment in order to prevent the hazards caused by lightning strikes through shielding and equipotential bonding. 5.4.6 This clause complies with the general requirements for determining the grounding resistance value for lightning protection impacts as specified in the current **standard, the Code for Design of Lightning Protection of Buildings GB 50057. 5.4.7 This clause complies with the principles specified in the current **standard \"Code for Design of Lightning Protection of Buildings\" GB 50057; the value of the comprehensive grounding resistance meets the requirement set out in the current **standard \"Safety Regulations for Tower Cranes\" GB 5144, which stipulates that the grounding resistance of cranes should not exceed 4Ω. 6 Distribution Rooms and Self-Provided Power Sources 6.1 Distribution Rooms 6.1.1 This section complies with the provisions of the current **standard, the ‘Code for Design of Low-Voltage Distribution Systems’ GB 50054. 6.1.2 This clause is in accordance with the provisions of the current **standard \"Design Code for Substations of 10 kV and Below\" GB 50053. 6.1.3 This clause meets the requirements for the construction of distribution rooms specified in the current **standard, ‘Design Code for Substations of 10 kV and Below’ GB 50053. 6.1.4 This clause is in compliance with the provisions of the current **standards, namely the ‘Design Code for Substations of 10 kV and Below’ GB 50053 and the ‘Design Code for Low-Voltage Distribution Systems’ GB 50054. 6.1.5 This clause is formulated in accordance with the current **standard \"Design Code for Electrical Measuring Instrument Installations in Power Equipment\" GBJ 63. 6.1.6 This clause is formulated in accordance with the current **standard \"Code for Design of Low-Voltage Power Distribution\" GB 50054, taking into account the need to ensure reliable control and protection of power supply circuits at construction sites, as well as the requirement to install leakage protection systems. Articles 6.1.7 to 6.1.9 are technical regulatory provisions designed to ensure the safe and reliable use of electrical systems at construction sites, as well as the safety during power outages for maintenance purposes and during the process of turning power on and off. 6.2 230/400V self-provided generator sets 6.2.1～6.2.3 These three clauses comply with the provisions of the current industry standard, the \"Code for Electrical Design of Civil Buildings\" JGJ/T 16. 6.2.4 The provisions of this article are consistent with Article 5.1.1. 6.2.5 This clause is in accordance with the provisions of the current **standard, ‘Design Code for Electrical Measuring Instrumentation in Power Installations’ GBJ 63. 6.2.6 This clause meets the general requirements of the current industry standard \"Code for Electrical Design of Civil Buildings\" JGJ/T 16, and further emphasizes the need to ensure power isolation as well as protection against short circuits, overloads, and electric leakage in construction electrical systems. 6.2.7 This clause complies with the requirements of the current **standard, the ‘Code for Safety of Power Supply and Consumption at Construction Sites’ GB 50194, regarding the installation of synchronization devices for parallel generators and the conditions for operating generators in parallel. 7 Distribution Lines 7.1 Overhead Lines 7.1.1 This section complies with the provisions of the current **standard, ‘Design Code for Overhead Power Lines of 66 kV and Below’ GB 50061. 7.1.2 This clause is in line with the provisions of the current standards, namely the \"Design Code for Overhead Power Lines of 66 kV and Below\" GB 50061 and the \"Safety Code for Power Supply and Use at Construction Sites\" GB 50194. Taking into account the actual conditions at construction sites, it emphasizes that dedicated utility poles should be used for overhead lines. 7.1.3 This section, in accordance with the current **standard \"Code for Design of Low-Voltage Power Distribution\" GB 50054 and taking into account the characteristics of electrical installations at construction sites, specifies the criteria for selecting the cross-sectional area of overhead line conductors as well as the minimum allowable values for such cross-sectional areas. 7.1.4 This clause is in line with the provisions of the current standards, namely the \"Design Code for Overhead Power Lines of 66 kV and Below\" GB 50061 and the \"Safety Code for Power Supply and Consumption at Construction Sites\" GB 50194, regarding the limitation on the number of conductor joints in overhead lines. The purpose is to prevent wire breaks, the subsequent collapse of utility poles due to those breaks, wires falling to the ground, as well as poor electrical contact, which could affect the safety and reliability of power supply. 7.1.5 This clause complies with the provisions of the current industry standard, the \"Code for Electrical Design of Civil Buildings\" JGJ/T 16, regarding the phase sequence arrangement of low-voltage overhead lines; taking into account the use of TN-S systems, uniform regulations on the installation location of the PE wire have been added. Sections 7.1.6 to 7.1.8 comply with the general provisions of the current **standard \"Code for Design of Overhead Power Lines of 66 kV and Below\" GB 50061; taking into account the characteristics of temporary power supply systems at construction sites, they specify the material and size requirements for the crossarms of overhead lines. 7.1.9 This clause is in line with the general provisions of the current **standard \"Code for Design of Overhead Power Lines of 66 kV and Below\" GB 50061; considering the poor environmental conditions at the construction site, some requirements are slightly higher than those specified in this standard. Points 7.1.10 and 7.1.11 are in line with the provisions of the current **standard, ‘Code for Safety of Power Supply and Use at Construction Sites’ GB 50194. 7.1.12 This clause is in accordance with the provisions of the current industry standard, the \"Code for Electrical Design of Civil Buildings\" JGJ/T 16. 7.1.13 It shall comply with the provisions of the current **standard, ‘Design Code for Overhead Power Lines of 66 kV and Below’ GB 50061. Points 7.1.14 and 7.1.15 are in line with the provisions of the current **standard \"Code for Safety of Power Supply and Consumption at Construction Sites\" GB 50194, as well as the current industry standard \"Code for Electrical Design of Civil Buildings\" JGJ/T 16. 7.1.16 This clause is in line with the relevant provisions of the current industry standard, the \"Code for Electrical Design of Civil Buildings\" JGJ/T 16. Taking into account the practice of installing strong-current and weak-current circuits on the same pole at construction sites, it specifies additional requirements regarding the spacing between overhead service lines and broadcast and telephone lines when they are laid together. Points 7.1.17 and 7.1.18 are in line with the principles set out in the current **standard \"Code for Design of Low-Voltage Power Distribution\" GB 50054 and the current industry standard \"Code for Electrical Design of Civil Buildings\" JGJ/T 16, by providing a slight additional safety margin for the protected power distribution circuits. 7.2 Cable Lines 7.2.1 This section complies with the current **standard \"Code for Design of Cables in Electrical Engineering\" GB 50217, as well as the current **standard \"Polyvinyl Chloride Insulated Cables with Rated Voltage of 450/750V and Below – Part 1: General Requirements\" GB 5023.1 (which is equivalent to IEC Standard IEC 227-1:1993 Amendment No.1 1995), and the current **standard \"Rubber Insulated Cables with Rated Voltage of 450/750V and Below – Part 1: General Requirements\" GB 5013.1 (which is equivalent to IEC Standard IEC 245-1:1994) regarding the requirements for cable conductors. Sections 7.2.2 to 7.2.4 are in accordance with the provisions of the current **standard, the ‘Code for Design of Cables in Electrical Engineering’ GB 50217. Sections 7.2.5 to 7.2.8 are in line with the principles set out in the current **standard \"Code for Design of Low-Voltage Power Distribution\" GB 50054 and the current industry standard \"Code for Electrical Design of Civil Buildings\" JGJ/T 16, by providing a slight additional safety margin for the protected power distribution circuits. 7.2 Cable Lines 7.2.1 This section complies with the current **standard “Code for Design of Cables in Electrical Engineering” GB 50217, as well as the current **standard “Polyvinyl Chloride Insulated Cables with Rated Voltage of 450/750V and Below – Part 1: General Requirements” GB 5023.1 (which is equivalent to IEC standard IEC 227-1:1993 Amendment No. 1995), and the current **standard “Rubber Insulated Cables with Rated Voltage of 450/750V and Below – Part 1: General Requirements” GB 5013.1 (which is equivalent to IEC standard IEC 245-1:1994) regarding the requirements for cable conductors. Sections 7.2.2 to 7.2.4 are in compliance with the provisions of the current **standard, the ‘Code for Design of Electrical Cables’ GB 50217. Sections 7.2.5 to 7.2.8 are in compliance with the current **standard \"Code for Design of Cables in Electrical Engineering\" GB 50217 and the current industry standard \"Code for Electrical Design of Civil Buildings\" JGJ/T 16. Among them, the higher requirements for the distance between buried cables and nearby external power cables as well as ducts are intended to ensure the safety of their installation. Furthermore, to meet the actual needs of the construction site and facilitate the inspection and maintenance of cable connectors, it is emphasized that these connectors should be placed in dedicated junction boxes on the ground. Articles 7.2.9 and 7.2.10 are formulated in accordance with the current standards such as the \"Code for Design of Cables in Electrical Engineering\" GB50217, the \"Code for Design of Low-Voltage Distribution Systems\" GB50054, the \"Code for Safety of Power Supply and Consumption at Construction Sites\" GB50194, as well as the industry standard \"Code for Electronic Design in Civil Buildings\" JGJ/T 16; they aim to take into account the actual conditions at construction sites and ensure the safe and reliable operation of cable systems. Among them, it is strictly prohibited to lay overhead cables along the scaffolding, and it is also forbidden for them to pass through the scaffolding; this is to prevent the scaffolding from becoming electrified due to mechanical damage to the cables. The measures to protect the power cables in the decoration and fitting section from mechanical damage and electrical hazards, by laying them along the floor at wall corners, involve using methods such as enclosing them in flame-retardant insulated tubes or cable trays. 7.3 Indoor Wiring Sections 7.3.1 to 7.3.3 comply with the provisions of the current **standard \"Code for Design of Low-Voltage Power Distribution\" GB 50054 and the current industry standard \"Code for Electrical Design of Civil Buildings\" JGJ/T 16. The term “indoor” as used here refers to the interior of all temporary facilities at the construction site, such as those used for office work, production, and living. Points 7.3.4 and 7.3.5 are in line with the current industry standard, the \"Code for Electrical Design of Civil Buildings\" JGJ/T 16; the requirements regarding the minimum cross-sectional area of insulated wires are slightly higher in this standard. 7.3.6 This clause is formulated in accordance with the current industry standard, the \"Code for Electrical Design of Civil Buildings\" JGJ/T 16. It sets slightly higher requirements for fixing wires using porcelain insulators, and adds additional requirements for fixing wires using porcelain clamps. 8 Distribution Boxes and Switch Boxes 8.1 Installation of Distribution Boxes and Switch Boxes 8.1.1–8.1.4 To comprehensively accommodate the sectional layout of electrical equipment at construction sites as well as their specific power usage patterns, and to enhance the safety and reliability of electricity supply, these four provisions, in accordance with the current **standard “Code for Design of Power Supply and Distribution Systems” GB 50052, specify the principles for three-level power distribution at construction sites, the requirement that each machine be equipped with its own switch and leakage protector within a separate box, and the principle of separating power distribution for mechanical equipment from that for lighting. The requirement for balanced three-phase loads is primarily aimed at reducing the asymmetry and voltage deviation in three-phase low-voltage distribution systems, thereby ensuring the quality of electrical power supplied. Articles 8.1.5 and 8.1.6, in accordance with the current standards **\"Guidelines for Electrical Safety\" GB/T 13869 and \"Safety Regulations for Power Supply and Use at Construction Sites\" GB 50194, and taking into account the conditions of work at construction sites, establish relevant restrictive provisions regarding the environmental conditions surrounding the installation locations of distribution boxes and switch boxes, in order to ensure their safe and reliable operation. 8.1.7 This clause specifies the unified material standards for distribution boxes and switch boxes, including a prohibition on the use of wooden distribution boxes and wooden switch boxes. 8.1.8 This clause is in accordance with the relevant provisions of the current standards **\"Code for Safety of Power Supply and Use at Construction Sites\" GB 50194 and \"Code for Design of Low-Voltage Distribution Systems\" GB 50054. To facilitate operation and maintenance, prevent damage from debris and splashed water on the ground, and adapt to the working conditions at construction sites, regulations have been set for the installation height of distribution boxes and switch boxes. 8.1.9～8.1.17 In accordance with the relevant provisions of the current standards such as the \"Guidelines for Electrical Safety\" GB/T 13869, the \"Safety Regulations for Power Supply and Use at Construction Sites\" GB 50194, and the \"Design Code for Low-Voltage Distribution Systems\" GB 50054, these 9 clauses establish comprehensive standardized requirements for the structural design of distribution boxes and switch boxes, in order to meet the conditions of outdoor work at construction sites as well as the needs related to zero-grounding protection in electrical systems. Among them, the installation dimensions of electrical appliances inside the enclosure are determined in accordance with the current **standard \"Insulation coordination of equipment in low-voltage systems – Part 1: Principles, requirements and tests\" GB/T 16935.1 (idt IEC 664-1:1992), as well as the requirements regarding electrical clearance and creepage distance specified in the \"Guidelines for the safe design of electrical equipment\" GB 4064. These dimensions are set taking into account the needs for convenient installation, maintenance, and operation of the electrical appliances. 8.2 Selection of electrical equipment 8.2.1 This clause complies with the provisions of the current **standard, ‘Guidelines for Electrical Safety’ GB/T 13869. 8.2.2 This section sets out comprehensive and standardized requirements for the electrical equipment in the main distribution box, in accordance with the general provisions of the current **standard \"Code for Design of Low-Voltage Power Distribution\" GB 50054, and taking into account the needs of temporary power supply systems at construction sites regarding power isolation as well as protection against short circuits, overloads, and electric leakage. Among them, the isolation device used as an isolating switch can be a knife-type switch or an isolation plug; it can also be a circuit breaker that features a clearly visible breaking point when it interrupts the circuit, such as the DZ20 series of circuit breakers with transparent plastic housings. These circuit breakers have transparent plastic covers through which the breaking point can be seen, and they can thus serve as isolating switches as well, eliminating the need for a separate isolating switch. Circuit breakers that do not have a clearly visible disconnection point when disconnected cannot be used as isolating switches. 8.2.3 This clause is in compliance with the current **standard \"Design Code for Electrical Measuring Instruments in Power Installations\" GBJ 63 and the current industry standard \"Code for Electrical Design of Civil Buildings\" JGJ/T 16. The prohibition against an open circuit in the secondary circuit of current transformers is intended to prevent the risk of electric shock caused by high voltages that may occur when the secondary circuit is open during operation. 8.2.4 This clause is in line with the current **standard \"Code for Design of Low-Voltage Power Distribution\" GB 50054. It meets the requirements for isolating, controlling the branch circuits of power distribution systems, as well as providing protection against short circuits and overloads. It also ensures safety and convenience during operation and maintenance; leakage protection devices are not required to be installed in distribution boxes. Sections 8.2.5 to 8.2.7 meet the requirements of the current standards **GB 50054 – Code for Design of Low-Voltage Power Distribution Systems**, GB 50055 – Code for Design of Power Supply Systems for General Electrical Equipment, and GB 13955 – Installation and Operation of Residual Current Devices; they are suitable for ensuring power isolation for electrical equipment as well as providing protection against short circuits, overloads, and residual currents. Among them, isolation appliances used as isolating switches refer to switch-blades, knife fuses, circuit breakers, and other electrical devices that can simultaneously disconnect all poles of the power supply and have a clearly visible breaking point when breaking the circuit. When appliances such as knife fuses or circuit breakers that have a visible breaking point are used and also possess overcurrent protection functions, it is not necessary to install separate overcurrent protection devices such as fuses or circuit breakers. Sections 8.2.10 to 8.2.14 comply with the provisions of the current standards **“General Requirements for Residual Current Devices” GB 6829, “Installation and Operation of Leakage Protection Devices” GB 13955, and “Effects of Electric Current on the Human Body – Part 1: Common Parts” GB/T 13870.1. Among them, the determination of the safety limit value of 30mA•s in clause 8.2.11 is primarily based on the current **standard \"Effects of electric current on the human body – Part 1: General aspects\" GB/T 13870.1, which specifies the time/current effect regions for sinusoidal alternating currents in the range of 1＜15～100Hz in China. 8.2.15 This clause is formulated in accordance with the current **standard ‘Guidelines for Electrical Safety’ GB/T 13869, taking into account the conditions of outdoor work at construction sites. It is strictly prohibited to use plugs and sockets for the movable connection of power supply leads, mainly to prevent accidental short circuits that could occur if a plug comes into contact with live electricity and falls off, as well as to avoid electric shock hazards resulting from direct human contact. 8.3 Use and Maintenance 8.3.1 This section specifies the names, purposes, and circuit divisions of distribution boxes and switch boxes in accordance with the current **standard \"Code for Safety of Power Supply and Consumption at Construction Sites\" GB 50194, primarily to prevent misoperations. Sections 8.3.2 to 8.3.4 are provisions established in accordance with the current **standard \"Guidelines for Electrical Safety\" GB/T 13869, taking into account the actual environmental conditions at construction sites, in order to ensure the safe operation of distribution boxes as well as the safety of maintenance activities. Among them, the regular inspection and maintenance intervals should not exceed one month. 8.3.5 This clause is in line with the general safety procedures for shutting down and restarting power supply in electrical systems, ensuring that the main distribution box and distribution panels remain in an unloaded state under normal conditions. 8.3.6 This clause is formulated in accordance with the current standards, namely the «Guidelines for Electrical Safety» GB/T 13869 and the «Safety Regulations for Power Supply and Use at Construction Sites» GB 50194, taking into account the actual conditions at construction sites. This includes turning off and locking the power switch box during lunch breaks, after work, or in cases of partial shutdowns lasting more than 1 hour, in order to prevent the equipment from being started accidentally. 8.3.7 This clause is formulated in accordance with the requirements of the current **standard, the ‘Safety Code for Power Supply and Use at Construction Sites’ GB 50194, regarding the knowledge and skills needed by personnel engaged in electrical work, and takes into account the actual conditions at construction sites. Articles 8.3.8 and 8.3.9 are stipulated in accordance with the current **standard \"Guidelines for Electrical Safety\" GB/T 13869, aiming to ensure the safe and reliable operation of distribution boxes and switch boxes, as well as to prevent the disruption of the three-level power distribution system and the requirement that each machine be equipped with its own switch, leakage protector, and box. Articles 8.3.10 and 8.3.11 are formulated in accordance with the current standards **\"Code for Design of Low-Voltage Power Distribution Systems\" GB 50054, \"Guidelines for Electrical Safety\" GB/T 13869, and the current industry standard \"Safety Regulations for Electric Power Construction\" DL 5009.2; they aim to ensure the proper electrical functioning of distribution boxes and switch boxes, as well as to protect their incoming and outgoing wires and connections from damage. 9 Electric construction machinery and hand-held electric tools 9.1 General provisions 9.1.1 These provisions are formulated in accordance with the current **standard \"Guidelines for Electrical Safety\" GB/T 13869, to establish common safety technical requirements for electric construction machinery and hand-held electric tools used in outdoor working conditions at construction sites. 9.1.2 This clause is formulated in accordance with the current **standard \"Code for Safety of Power Supply and Consumption at Construction Sites\", GB 50194, and specifies comprehensive grounding measures that take into account the requirements for neutral grounding protection for large-scale mechanical equipment, lightning protection and grounding, as well as repeated grounding of the PE wire. 9.1.3 This clause is in line with the provisions of the current **standard \"Safety of hand-held electric tools – Part 1: General requirements\" GB 3883.1 (which is equivalent to the International Electrotechnical Commission standard IEC 745-1) regarding the fact that for Class II and Class III tools, protection against electric shock relies primarily on double insulation (reinforced insulation) and supply at safely low voltage (SELV). 9.1.4 This clause is in line with the current **standard \"Code for Design of Cables in Electrical Engineering\" GB 50217, and meets the requirements of the TN-S neutral protection system. Three-phase electrical equipment is equipped with single-phase appliances; for example, indicator lights are single-phase appliances. 9.1.5 This clause is in compliance with the current **standard, the Code for Design of Power Distribution of General Electrical Equipment GB 50055. 9.2 Lifting Machinery 9.2.2 This clause complies with the current **standard \"Code for Construction and Acceptance of Electrical Installations in Lifting Machinery\" GB 50256, the \"Safety Regulations for Tower Cranes\" GB 5144, as well as the current industry standard \"Safety Regulations for Power Construction\" GB 5009. 9.2.4 This clause is formulated in accordance with the current **standard, the ‘Code for Safety of Power Supply and Use at Construction Sites’ GB 50194. Sections 9.2.5 to 9.2.7 are in line with the provisions of the current **standard, the Safety Regulations for Tower Cranes GB 5144. Among them, the insulation and grounding measures for preventing electromagnetic wave induction are primarily aimed at protecting people from electric shock. 9.2.8～9.2.12 The safe operation of outdoor elevators relies, in terms of electricity, on advanced electrical control technologies and mechanical-electrical interlock devices; relevant provisions have been made in these clauses to address this matter. 9.3 Pile-driving Machinery 9.3.1 This section complies with the current **standard \"Protection Degrees for Enclosures (IP Code)\” GB 4208. An IP68 protection level represents the highest level of protection against the entry of solid particles (dust-proof) and against the harmful effects of water intrusion (continuous submersion), and it is suitable for the operating conditions of motors in submersible drilling machines. 9.3.2 The provisions of this section refer to selecting the cable model in accordance with the current **standards (i.e., the International Electrotechnical Commission standard IEC 245-1:1994 \"Rubber-insulated cables for rated voltages up to 450/750 V – Part 1: General requirements\" and Appendix C of GB 5013.1), in order to suit the operating conditions of submersible motors. 9.3.3 These provisions specify the requirements for leakage protection under the working conditions of submersible drilling machines. 9.4 Ramming Machinery 9.4.1 The provisions of this section apply to ramming machinery that may operate in humid environmental conditions. 9.4.2 This clause is designed to accommodate the high-vibration operating conditions of ramming machinery, thereby enhancing the reliability of the electrical connection between the PE wire and the metal casing of the ramming machinery. 9.4.3 Same as the explanation in clause 9.3.2. 9.4.4 and 9.4.5: Earthfilling machinery generates intense vibrations during operation, causing the cables to move as well; this increases the risk of electric leakage as well as damage or breakage of the cables. The purpose of these provisions is to enforce proper insulation measures and operating procedures for operators, thereby preventing accidental electric shocks. The requirement that the cable length should not exceed 50m refers to the limitation on the size of the work area when the ramming machine is operating around its switch box. 9.5 Welding Equipment 9.5.1 This clause complies with the current **standard \"Code for Safety of Power Supply and Use at Construction Sites\" GB 50194 and the current industry standard \"Safety Regulations for Electric Power Construction\" DL 5009.2. Considering that welding sparks may ignite flammable and explosive materials and cause fires, these regulations include requirements for removing such flammable and explosive materials from the area around the welding site. Clauses 9.5.2 to 9.5.5 are in line with the provisions of the current standards **\"Code for Design of Power Distribution of General Electrical Equipment\" GB 50055 and \"Code for Safety of Power Supply and Use at Construction Sites\" GB 50194. In AC welding machines, in addition to installing a primary-side leakage protector in the switch box, a shock protection device must also be installed on the secondary side, in order to prevent electric shock hazards that may arise from the secondary-side no-load voltage of the welding machine. Currently, JZ-type arc welder electric shock protectors are widely used at construction sites; they can provide electric shock protection for both the primary and secondary sides. 9.6 Handheld electric tools Sections 9.6.1 to 9.6.4 are in line with the current **standard (namely the International Electrotechnical Commission standard IEC 745-1) ‘Safety of handheld electric tools – Part 1: General requirements’, GB 3883.1, as well as the current **standards ‘Safety technical regulations for the management, use, inspection, and maintenance of handheld electric tools’ GB 3787 and ‘Guidelines for electrical safety’ GB/T 13869. Narrow spaces refer to places such as boilers, metal containers, sewers, and pipes. The electric shock protection of Class I equipment relies not only on basic insulation but also includes a protective neutral or grounding measure, ensuring that exposed conductive parts do not become live in the event of damage to the basic insulation. The electric shock protection of Class II equipment relies not only on basic insulation but also includes additional double insulation or reinforced insulation; it does not provide protective earthing or grounding, nor is it dependent on the conditions of the equipment, and the enclosure is marked with a “⚪” symbol. Class II tools are further divided into two types: Class II tools with insulated material enclosures and Class II tools with metal material enclosures. The electric shock protection of Class III tools relies on safe extra-low voltage power supply, with no voltage higher than the safe extra-low voltage being generated within the tool. 9.7 Other electric construction machinery 9.7.1 This section complies with the current industry standard \"Technical Regulations for Safety in the Use of Construction Machinery\" JGJ 33, and meets the requirements regarding the installation of leakage protectors for the various electric machines listed, in their respective operating environments. 9.7.2 This clause is formulated in accordance with the current **standard \"Cables with rubber insulation, rated voltage 450/750 V – Part 1: General requirements\" GB 5013.1 (which is equivalent to the International Electrotechnical Commission standard IEC 245-1:1994), so as to ensure that the performance of the cables used meets the requirements of the operating environment conditions of various electric machinery. 9.7.3 This clause meets the requirements of the current industry standard, the \"Technical Regulations for Safety in the Use of Construction Machinery\" JGJ 33. 10 Lighting 10.1 General Provisions 10.1.1 This section complies with the current **standard \"Code for Design of Building Lighting\" GB 50034, and is suitable for the lighting requirements at construction sites. 10.1.2 In accordance with the current **standard ‘Code for Design of Building Lighting’ GB 50034, the lighting fixtures selected shall meet the requirements of high reliability during construction, the need to avoid frequent switching on and off, and energy efficiency. 10.1.3 This clause is in compliance with the current **standard \"Code for Design of Building Lighting\" GB 50034 and the current industry standard \"Code for Design of Urban Road Lighting\" GJJ45. 10.1.4 This clause complies with the requirements in the current **standard ‘Guidelines for Electrical Safety’ GB/T 13869 regarding the verification of the integrity of general electrical installations prior to their use. 10.1.5 The individual lighting power supply plan specified in this clause may be prepared in accordance with the requirements of this chapter and taking into account the actual conditions on site. 10.2 Lighting Power Supply 10.2.1 In accordance with the relevant provisions of the current **standard, the ‘Code for Design of Building Lighting’ GB 50034, and taking into account the environmental conditions of various lighting areas at construction sites, this section sets specific restrictions on the voltage required for lighting supply in different types of areas. 10.2.2, 10.2.3 These clauses are in accordance with the current **standard \"Code for Design of Building Lighting\" GB 50034. Taking into account the mobility and exposure of field lights as secondary lighting sources, restrictive provisions are set for their supply voltage and lamp structure in order to prevent accidents such as accidental electric shock or electrical fires caused by defects in the lamps. Safe extra-low voltage refers to a voltage in a circuit isolated from the power supply by a safe isolation transformer, where the AC effective value between conductors or between any conductor and ground does not exceed 50 V, or the DC ripple value does not exceed a certain limit. The DC ripple value is provisional. In cases with special requirements, especially when direct contact with live parts is permitted, a maximum voltage limit of 50 V below the RMS value for AC or the pulsating value for DC can be specified. This voltage limit should not be exceeded, whether the device is loaded or unloaded. 10.2.4 This clause is in compliance with the current **standard, the ‘Design Standard for Building Lighting’ GB 50034. 10.2.5 This clause is in line with the provisions of the current **standard, the ‘Safety Code for Power Supply and Use at Construction Sites’ GB 50194, regarding portable lamp transformers. It also emphasizes the prohibition of using autotransformers, as there is an electrical connection between their primary and secondary windings; moreover, since the voltage on the secondary side can be adjusted, this can lead to unstable voltage levels. In addition, winding failures can cause the higher voltage on the primary side to be transmitted to the secondary side, resulting in the destruction of lamps and electric shock. 10.2.6 This clause is in accordance with the provisions of the current **standard, the ‘Design Code for Building Lighting’ GB 50034. 10.2.7 This clause is formulated in accordance with the current standards, namely the **Guidelines for Electrical Safety GB/T 13869 and the Code for Safety of Power Supply and Use at Construction Sites GB 50194. The length of the power cable on the primary side of the transformer should not exceed 3 meters, mainly to keep it close to the switch box for easier operation and control. 10.2.8 This clause is in line with the relevant provisions of the current **standards such as the \"Code for Design of Building Lighting\", GB 50034, the \"Code for Design of Low-Voltage Power Distribution\", GB 50054, and the current industry standard the \"Code for Electrical Design of Civil Buildings\", JGJ/T 16. 10.3 Lighting fixtures 10.3.1 This clause complies with the principles specified in the current **standard \"Guidelines for Electrical Safety\" GB/T 13869, and is in line with the requirements regarding neutral grounding protection and leakage protection for electrical equipment as stipulated in Chapter 8 of these specifications. 10.3.2 The provisions in this clause regarding the installation height of indoor and outdoor lighting fixtures, as well as the safe distance between these fixtures and flammable materials, are in line with the current standards **“Safety Code for Power Supply and Use at Construction Sites” GB 50194 and “Standard for Lighting Design in Buildings” GB 50034. 10.3.3 This clause is in compliance with the current **standards, namely the «Code for Design of Building Lighting» GB 50034 and the «Code for Acceptance of Construction Quality of Building Electrical Engineering» GB 50303. 10.3.4 This provision is formulated in accordance with the current **standard, the ‘Code for Design of Building Lighting’ GB 50034. Since the electromagnetic ballasts used with fluorescent lamps generate heat during operation, this provision is intended primarily to prevent flammable materials from catching fire in the event that the ballast overheats or gets damaged due to a short circuit. Clauses 10.3.5 and 10.3.6 are in line with the provisions of the current **standard, the ‘Code for Construction and Acceptance of Electrical Lighting Installations in Electrical Equipment Installation Projects’ GB 50259. 10.3.7 This clause is in compliance with the provisions of the current **standards, namely the ‘Guidelines for Electrical Safety’ GB/T 13869 and the ‘Code for Construction and Acceptance of Electrical Lighting Installations in Electrical Equipment Installation Projects’ GB 50259. Articles 10.3.8 and 10.3.9 are formulated in accordance with the current standard \"Code for Construction and Acceptance of Electrical Lighting Installations in Electrical Equipment Installation Projects\" GB 50259, to address the lighting conditions in outdoor construction sites as well as the safety control requirements for temporary lighting installations. 10.3.10 This clause is in compliance with the current **standard \"Code for Safety of Power Supply and Use at Construction Sites\" GB 50194 and the current industry standard \"Safety Work Procedures for Electric Power Construction\" DL 5009.2. 10.3.11 This provision primarily emphasizes the need to install night-time warning lighting for tall construction projects that pose a risk to external safety at the construction site, as well as for construction machinery and areas where trenches or foundations are being dug. It also requires that the power supply for such warning lighting be reliable. The use of red warning lights is in accordance with the provisions of the current **standard ‘Safety Colors’ GB 2893**
A temporary power usage safety management system should be established by considering both power distribution safety and safe electricity use; I am also working on it recently. Hehe
When using temporary electricity, we need to issue a temporary electricity safety work permit