Electrical Safety Checklist

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Electrical Safety Checklist Instructions 1) Electrical systems pose a risk of electric leakage and electric shock. Therefore, the various measures taken to protect operators from electric shock must be effective and reliable, and must be applied in all aspects of the electrical system. Secondly, it is necessary to strictly adhere to electrical operation procedures as well as the supervision system for maintenance work. 2) In the event of an electric shock, the power supply must be cut off immediately, and artificial resuscitation must be carried out promptly and correctly. 1. Equipment inspection 1.1 Layout of the substation, building structure, and related facilities: 1.1.1 Substations should be avoided in locations where there is a risk of fire, explosion, air pollution, or severe vibrations ； 1.1.2 Substations are generally built with brick structures and have cement floors. The ground should be 150–300 mm higher than the surrounding ground to prevent water accumulation ； 1.1.3 The doors of the substation rooms shall open outward, and shall be made of lightweight iron doors or wooden doors covered with iron sheeting ； 1.1.4 Cable trenches, cable tunnels, etc., that are connected to substation buildings shall have measures to prevent rainwater and groundwater from seeping in as well as to prevent small animals from entering, and the covers for these cable trenches shall be made of non-flammable materials ； 1.1.5 Around the transformers in outdoor substations, the height of the fixed fences is 1.7 m or more. There should be a distance of 0.3 m or more between the bottom of the transformer and the ground. When two transformers are installed, the distance between them must be 1.5 m or more ； 1.1.6 High-voltage distribution installations can be installed separately; when there are fewer than 4 high-voltage switchgear units, the high-voltage and low-voltage distribution installations can be placed in the same room. When arranged in a single row, the distance between the two should be 2m or more ； 1.1.7 The transformer room should be well-ventilated; the ventilation openings should be fitted with cement or metal louverings, and metal screens with a mesh size of 10 mm or less should be installed on the inside to ensure safe operation in all seasons ； 1.1.8 The doors of the transformer room shall be locked, and warning signs stating “High Voltage – Danger” as well as safety color markings shall be installed ； 1.1.9 Minimum passage width for indoor distribution installations: 1.5 m for the operating passage in a single row layout, and 0.8 m for the maintenance passage ； The operating passage for the double arrangement is 2m, while the maintenance passage is 1m ； 1.1.10 The height of the enclosures for power transformation and distribution equipment should be no less than 1.7m. 1.2 Electrical equipment: 1.2.1 Transformers 1.2.1.1 The transformer enclosure shall have no oil seepage or leakage, and it shall be reliably grounded together with the core. 1.2.1.2 The operation of the transformer should be stopped if any of the following conditions are observed: 1) Unusual noises, such as uneven sounds or explosive noises ； 2) When the oil level is below the lower limit of the oil gauge and continues to drop due to oil leakage ； 3) When the explosion-proof tube or oil pillow leaks oil ； 4) Excessively high temperature under normal conditions, with a continuous rise ； 5) The oil color is too dark, with carbon present in the oil ； 6) The sleeve shows discharge or severe cracks. 1.2.2 Oil switches and isolating switches 1.2.2.1 The oil level in the oil switch should be between the upper and lower limits ； Oil color is normal, with no leaks ； The exhaust pipe should be in good condition ； 1.2.2.2 The oil switch operates flexibly, with accuracy and reliability, and the mechanical indication for closing is correct ； 1.2.2.3 For the oil switch after a fault-induced trip, it is necessary to check whether the bushing is fractured, whether the leads are burned, and whether the oil tank is deformed ； 1.2.2.4 The operating mechanisms of oil switches and isolating switches shall be equipped with reliable interlocking devices to ensure that the oil switch can be closed only after the isolating switch has been closed first ； When turning off the power, the oil switch must be turned off first before the isolating switch can be turned off ； 1.2.2.5 The insulator porcelain bottles and connecting rods of the disconnector shall be free of cracks, discharge marks, and the pins shall not be loose. 1.2.3 Load switches and fuses 1.2.3.1 Load switches should be used only for turning off and on normal circuits, and their arc-quenching devices must be in good condition. During closing, the contacts should move in unison, with the difference between successive phases not exceeding 3 mm ； 1.2.3.2 The load switch operating mechanism shall be flexible and reliable ； 1.2.3.3 After a drop-type fuse is disconnected, the vertical distance between its live parts and the ground should be at least 4.5 m in outdoor areas, and at least 3 m in indoor areas ； 1.2.3.4 Drop-type fuses should be installed at an angle, with a deviation of 15° to 30° from the vertical line ； 1.2.3.5 Fall protection devices cannot be used in areas where there is a risk of explosion, fire, or severe vibrations ； 1.2.3.6 All components of the switches shall be intact, the operating mechanisms shall be safe and reliable, and there shall be markings indicating the rated voltage, current values, and opening/closing positions. 1.2.4 Instrument Transformers 1.2.4.1 Voltage transformers are equipped with fuses for protection on both the primary and secondary sides (an automatic switch can be used on the secondary side); after the primary side switch is disconnected, measures should be in place in the secondary circuit to prevent voltage feedback ； 1.2.4.2 If a voltage transformer exhibits abnormal conditions such as noise, discharge sounds, smoke, or an unpleasant odor inside it, the power supply must be shut down to address the issue. The faulty circuit should not be disconnected using a disconnect switch; instead, the oil circuit breaker at the higher level must be turned off ； 1.2.4.3 The cross-sectional area of the wires in the secondary circuit of the current transformer is 2.5 mm²; there are no intermediate joints, the connections are reliable, and no switches or fuses shall be installed. 1.2.5 Power capacitors 1.2.5.1 Capacitors shall not be installed in areas with high temperatures, dust, humidity, or gases that are explosive, flammable, or corrosive ； 1.2.5.2 When the capacitor enclosure shows severe oil leakage, bulging, serious discharge from the porcelain bushing, sparking noises, or severe overheating, it should be taken out of service immediately ； 1.2.5.3 The capacitor room should have temperature controls, with the room temperature not exceeding 40°C; otherwise, mechanical ventilation should be installed. The capacitor housing temperature shall not exceed 60℃ ； 1.2.5.4 For capacitor banks in operation, the three-phase currents should remain balanced, with the current imbalance between phases not exceeding 5% ； 1.2.5.5 The capacitor bank shall be equipped with under-voltage protection, enabling it to be automatically disconnected from the power grid when the bus voltage drops to about 60% of the set value ； 1.2.5.6 For capacitors installed outdoors on the ground, the lower part of these capacitors should be at a height of 0.4 m or more above the ground level. The ground surface must have moisture-proof measures in place, and a mesh fence with gaps no larger than 20×20 mm should be installed around them, with a height of 1.7 m or more. The capacitor room should be well-ventilated, and the air intake windows should be equipped with steel grids having a mesh size of no more than 10×10 mm ； 1.2.5.7 Capacitors shall have reliable short-circuit holding devices and overload protection devices ； 1.2.5.8 The capacitor bank shall be equipped with a discharge circuit. Closing with charge is prohibited. After the capacitor stops operating, it must be discharged for at least 3 minutes before it can be closed again. 1.2.6 Cables 1.2.6.1 Minimum allowable distances between cables and the ground as well as buildings: 1) Burial depth of directly buried cables (from the ground surface to the cable’s outer cover) ； 0.7m for 1～35kV ； 2) The cable sheath is 0.6m above the underground foundation of the building. 1.2.6.2 Minimum clear distance when cables are close to each other: 1) 0.1 m for cables below 10 kV, and not less than 0.25 m for cables between 10 and 35 kV ； 2) The distance between cables used in different departments, including communication cables, is 0.5m. 12.6.3 Minimum allowable distance between cables and underground pipelines for approach and crossing ； 1) The clear distance between the cable and thermal pipelines is 2 m when they are close to each other, and 0.5 m when they intersect ； 2) The clear distance between the cable and other pipes when they are close to or intersecting is 0.5 m. 1.2.6.4 The clear distance between intersecting cables is 0.5 m ； 1.2.6.5 The excavated cables shall be suspended with wooden planks as padding, and the distance between the suspension points shall not exceed 1.5 m. Cables must not be suspended directly with wires and ropes without using supports ； 1.2.6.6 The metal outer sheaths of armored cables or cables with lead or aluminum covering shall be reliably grounded at both ends, and the grounding resistance shall not exceed 10 ohms ； 1.2.6.7 The sections of cables that pass through road surfaces and buildings, as well as those that extend below a height of 2 meters above the ground, must be placed within protective tubes; the inner diameter of such tubes should be no less than 1.5 times the outer diameter of the cables ； 1.2.6.8 Markers indicating the direction of the cables should be installed on the ground where they are laid, to facilitate operation and maintenance. 1.2.7 Lighting fixtures and portable electrical appliances 1.2.7.1 The insulation resistance of all portable electrical appliances shall be no less than 2 MΩ, and the wires and plugs shall be intact. The wiring must be made of tough rubber wire or flexible wire with plastic insulation, with three wires for single-phase appliances and four wires for three-phase appliances; the cross-sectional area should be at least 0.5 mm2. The wiring must not have any joints and should not be too long, generally not exceeding 5 meters ； 1.2.7.2 All portable electrical tools should be equipped with leakage protection devices whose leakage operating current is 30 mA or less and whose operating time is 0.1 s or less ； 1.2.7.3 Low-voltage wiring installations of 36V or less should be neat and organized, and all sockets must be dedicated sockets ； 1.2.7.4 All lighting fixtures, switches, and plugs must meet the requirements of the surrounding environment; in locations such as those with high humidity, corrosive vapors and gases, areas prone to fire and explosion, or outdoor areas, appropriate lighting fixtures and switches with moisture-proof, explosion-proof, and rainproof properties should be used accordingly ； 1.2.7.5 The height of 220V lamp holders above the ground shall comply with the following requirements: 1) In humid, hazardous areas and outdoors, it shall be no less than 2.5 m ； 2) Production workshops, offices, etc. should generally be no less than 2m ； 3) When it must be lowered, it should not go below 1m; however, the lamp cord from the lamp base to a height of 2m above the ground must be fitted with insulating sleeves, and protective measures must be taken for the lamp. 1.2.7.6 Switches and sockets should be at a height of not less than 1.3m above the ground. The socket can also be installed low, but it should not be lower than 15 mm from the ground ； 1.2.7.7 The operating voltage for local lighting and portable hand lamps shall be a suitable safe voltage selected according to their operating environment. The lighting fixtures on machine tools or bench workbenches should use a low voltage of 36V or less ； The voltage of the lighting fixtures inside boilers, evaporators, and other metal containers must not exceed 12V. The insulation strength of the wires and electrical fixtures for low-voltage lamps shall be no less than 250V AC ； 1.2.7.8 The socket or switch shall be intact and undamaged, firmly installed; its housing or cover shall be in good condition, it shall operate smoothly, and the connections shall be reliable ； 1.2.7.9 Outdoor lighting fixtures and switches should be of rainproof type, and their installation must be firm and reliable ； 1.2.7.10 Do not pull or connect temporary wires and lights randomly. Temporary line applications must be filed as required by production needs; regular inspections should be carried out, and the lines must be removed upon expiration ； 1.2.7.11 Temporary wires are well-insulated rubber wires, installed suspended or along walls. During installation, the height above the ground indoors must be no less than 2.5 m, and outdoors it must be no less than 3.5 m. The distance between temporary wires and equipment, water pipes, hot water pipes, doors, and windows should be at least 0.3 m; at intersections with roads, this distance should be no less than 6 m. 1.3 Overhead lines and indoor/outdoor wiring 1.3.1 The cross-sectional area of the conductors must meet the requirements for mechanical strength. The spacing between wires and the distance from surrounding facilities, as well as the height above the ground when they pass overhead, must comply with relevant regulations ； 1.3.2 Overhead lines must not cross the roofs of flammable buildings ； 1.3.3 The tensioning wire should be installed at the point of force application in the opposite direction to the direction in which the conductor is laid, or at the point where the combined forces resulting from uneven tension act. The direction of the pull wire should be aligned with that of the circuit. The angle tie wire should be aligned with the angle bisector of the line. The wind-resistant tie rod is perpendicular to the line ； 1.3.4 The angle between the utility pole and the guy wire shall be no less than 45°; in cases where environmental constraints apply, it shall be no less than 30° ； 1.3.5 When different lines share the same pole, the low-voltage lines shall be located below the high-voltage lines, and the distance between the two ends of a 10KV straight pole shall be no less than 1m. The communication and broadcasting lines are located below the low-voltage lines. The spacing between them shall be no less than 1.5m. Low-voltage lines are arranged in multiple layers; the distance between layers of straight poles should be no less than 0.6 m, the distance between adjacent conductors should be no less than 0.4 m, and the distance at branches or corners should be no less than 0.3 m ； 1.3.6 In a three-phase four-wire power supply system, the cross-sectional area of the neutral wire shall be no less than half of that of the phase wires in the circuit. It shall be not less than the minimum allowable cross-sectional area; in single-phase systems, the cross-sectional area of the neutral wire is the same as that of the phase wires ； 1.3.7 Wires of different voltages and frequencies shall not be inserted into the same metal tube. (The voltage of all circuits on the same device and in the same unit is below 66V, except for three-phase four-wire lighting circuits) ； 1.3.8 When wiring metal pipes, the inside of the pipes and their openings must be smooth without burrs, and they must be properly connected to ground ； 1.3.9 The wires of indoor and outdoor exposed wiring installations shall be protected by porcelain tubes, steel tubes, or plastic when passing through walls. Protect it with steel pipes or rigid plastic pipes when passing through floor slabs. Plastic pipes leading to the outdoors should be used one per line. When the two circuits intersect, an insulating tube should be fitted over the conductors of one of the circuits that are close to the installation surface. 1.4 Lightning Protection and Grounding 1.4.1 Low-voltage lines, communication lines, and broadcasting lines are strictly prohibited from being installed on buildings equipped with lightning rods ； 1.4.2 The installation of lightning rods shall meet the requirements for mechanical strength and corrosion resistance. Lightning rods should be made of steel pipes with a diameter of not less than 25 mm and a wall thickness of not less than 2.75 mm, or round steel bars with a diameter of not less than 20 mm, and they should be galvanized ； 1.4.3 The wiring for lightning rods shall use galvanized stranded wire with a cross-sectional area of 35 mm2 or more ； 1.4.4 Lightning protection strips or nets should preferably be made of galvanized steel. The minimum diameter of round steel is 8 mm; the thickness of flat steel should be no less than 4 mm, with a cross-sectional area of no less than 60 mm2 ； 1.4.5 Valve-type arresters should be installed vertically, with good sealing; there should be no cracks at the porcelain seals or at the joints, and no abnormal noises should be heard when gently shaking them. If the grounding wire is made of copper, its cross-sectional area should be 16 mm2 or greater ； If it is an aluminum wire, it should be 25 mm2 or greater ； 1.4.6 Lightning protection systems should be regularly inspected and subjected to preventive tests; lightning receptors and downconductors should be replaced if they are corroded by more than 30% ； 1.4.7 Grounding protection shall be employed in three-phase three-wire supply systems with a neutral point that is not directly grounded ； 1.4.8 In three-phase four-wire supply systems with the neutral point grounded, neutral grounding protection shall be employed; the transformer’s neutral point shall be grounded for operation, and repeated grounding shall be provided every kilometer along the overhead branch lines and main lines as well as at the endpoints ； 1.4.9 In low-voltage power supply systems with neutral grounding protection, repeated grounding shall be provided at the distribution cabinets where cables and overhead lines enter. Fuses and switches are not allowed to be installed on the neutral wire ； 1.4.10 In the same low-voltage power supply system, the enclosures of some equipment should not be connected to neutral while those of other equipment should be protected by grounding ； 1.4.11 For all electrical equipment and electrical installations that may have hazardous voltages due to insulation failure, their metal enclosures and frames must be reliably grounded, with the grounding resistance R being less than or equal to 4Ω ； 1.4.12 The grounding electrodes shall be galvanized, and their cross-sectional area shall meet the following requirements: ① Minimum cross-sectional area for lightning protection grounding electrodes: round steel with a diameter of 10 mm ； Angle steel 50×50×5mm ； The flat steel is 4 mm thick with a cross-sectional area of 100 mm2 ； The steel pipe has a thickness of 3.5 mm and a diameter of 50 mm. ② The minimum cross-sectional area for a general grounding electrode is: 8 mm in diameter for round steel. Angle steel thickness: 4mm ； The flat steel is 4mm thick. Cross-section 48mm2 ； The thickness of the steel pipe is 3.5 mm². ③ The minimum cross-sectional area of the grounding main wire in a general grounding system: diameter of the round steel bar is 6 mm ； Angle steel thickness: 3mm ； Flat steel cross-section: 24mm2 ； 1.4.13 The grounding resistance of various grounding devices shall comply with the following requirements: ① In systems with high earth short-circuit currents: R≤2000/I; when I＞400A, R≤0.5Ω. ② In systems with low earth short-circuit currents: when high-voltage and low-voltage equipment are used together, R≤120/I, with a value generally not exceeding 10Ω; when used only for high-voltage equipment, R≤250/I, with a value generally not exceeding 10Ω. ③ In low-voltage power systems: when the total capacity of the electrical equipment operating in parallel is 100 kV or more, R≤4Ω ； If it is 100 kVA or less, repeat the test; the ground resistance R should be ≤ 10 Ω. 2. Behavioral safety 2.1 Equipment inspections must not be carried out alone; inspections are only permitted outside the barriers surrounding high-voltage equipment. It is also forbidden to walk under the high voltage of the transformer ； 2.2 When maintaining electrical equipment, it is necessary to shut off the power supply, verify that there is no electricity present, and then discharge and ground the equipment. Install barriers and hang safety signs ； 2.3 When operating or maintaining electrical equipment, insulating shoes and gloves, protective glasses must be worn as required, along with insulating mats and insulating tools ； 2.4 Electrical maintenance work should be carried out under supervision, with one person operating and another person supervising ； 2.5 During an emergency power outage, it is prohibited to enter the barriers or touch the conductive parts of the equipment without taking safety measures ； 2.6 In the event of electric shock or fire, immediately cut off the power supply and carry out rescue efforts ； 2.7 Electrical safety tools must be fully equipped, regularly tested, used only when they meet the specified standards, and properly stored after use ； 2.8 Strictly abide by electrical safety operating procedures, the systems for switch operation tickets and maintenance work tickets, the work permit system, the work supervision system, the systems for work interruptions and completions, the shift handover system, as well as the fire safety and equipment management systems and access control systems, among others. 2.9 When working on low-voltage equipment while it is still powered on, a dedicated supervisor must be assigned, and the live parts of adjacent phases should be separated using insulating boards. Disable tools such as files and metal rulers ； 2.10 Outside line electricians are strictly prohibited from working on poles or performing switch operations in conditions such as winds of force 6 or higher, heavy rain, or thunderstorms. 3. The indoor area should be equipped with carbon dioxide, carbon tetrachloride, dry powder fire extinguishers, or sand boxes, and the operators should be familiar with their use. This post was last edited by zhx7540 on 2007-12-6 12:23.]