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Chapter 1 General Provisions Article 1 These regulations apply to power cables and control cables of all voltage levels. The technical standards for cables shall meet the requirements of electrical engineering standards. The regulations regarding cable installations and testing shall be in accordance with the relevant professional codes. Article 2 For cable lines with a voltage of 2000 volts or higher, where the total length exceeds 50 kilometers, it is necessary to calculate the accident rate and maintenance cost rate on an annual basis: Accident rate = 100N/L, incidents per hundred kilometers per year; Maintenance cost rate = 100Y/L, 10,000 yuan per hundred kilometers per year. Here, L represents the total length of the cable lines with a voltage of 2000 volts or higher, in kilometers ； N is the number of times that these cable lines were unable to supply power during operation in that year due to the activation of protective devices or warning signals, etc.; Y is the total cost of maintenance and operation for these cable lines in that year (in RMB, in ten thousand units). Section 1: Basic Requirements for Cable Lines Article 3: The long-term allowable oil pressure for oil-filled cables with low oil pressure is 0.5 to 3 kilograms per square centimeter. Article 4: The maximum allowable height difference between the highest and lowest points of a cable route shall not exceed the values specified in Table 1. Article 5: If the horizontal difference between the highest and lowest points of a cable route exceeds the limits set out in Article 4, plug-type connectors may be used. Article 6: The bending radius of cables shall be not less than the following values: 1. For paper-insulated multi-core power cables (with lead coating or armor), 15 times the outer diameter of the cable ； 2. Paper-insulated single-core power cable (with lead sheath, armored or unarmored): 20 times the outer diameter of the cable ； Table 1 Voltage, with or without armor; lead-clad, aluminum-clad; 1–3 kV: armored, unarmored; 25 meters, 20 meters, 25 meters, 25 meters; 6–10 kV, 20–35 kV: armored or unarmored; 15 meters, 5 meters, 20 meters. Note: 1. The lowest point of an underwater cable line refers to the level at the lowest water level ； 2. The maximum allowable height difference for rubber and plastic cables is not restricted by this table ； 3. The allowable height difference for oil-filled cables is determined based on their long-term allowable oil pressure. 3. Aluminum-clad cables, rubber-insulated and plastic-insulated cables, as well as control cables (with lead cladding or plastic coating) shall comply with the manufacturer’s specifications. Article 7 does not permit operating one of the three cores in a three-core cable at ground potential. In a three-phase system, when using single-core cables, the determination of the distance between these cables requires taking into account various factors such as the induced voltage in the metal shielding or outer shield layer and the losses resulting therefrom, the risk that a breakdown in one phase could affect adjacent phases, the width of the space occupied by the cables in the conduit, and the convenience of maintenance. Except for oil-filled cables and underwater cables, single-core cables should be arranged to form as close-packed equilateral triangles as possible. Article 8: In single-core cables, the lead sheath is only grounded at one end; the normal induced voltage at the other end of the lead sheath should generally not exceed 65 volts. When this normal induced voltage exceeds 65 volts, the exposed parts of the lead sheath that are likely to come into contact with people, as well as the equipment connected to it, must be properly shielded, or the lead sheaths can be insulated in sections and then interconnected for the three phases. If a single-core cable is equipped with a metal reinforcement strip in the lead sheath, this reinforcement strip should be connected to the lead sheath so that both are at the same electrical potential ； For armored single-core cables that lack a reliable outer protective layer, in any situation such cables must have both the lead coating and the ends of the armor wires grounded. Article 9: In single-core cable circuits where the lead shielding has only one point of grounding, insulation protectors for the shielding should be installed at all points where the maximum induced voltage approaches the breakdown strength of the shielding insulation; such protectors can include nonlinear valve elements or ball gaps. In single-core cable circuits connected to overhead lines, where the lead sheath is grounded at only one point, it is preferable to ground it on one side of the overhead line. When a single-core cable circuit has only one point for grounding the lead sheath, it is advisable to consider laying an insulated return wire in parallel with both ends grounded ； The impedance of the return line should be matched as closely as possible to the maximum zero-sequence current and the induced voltage on that return line. The arrangement of the return paths should minimize the losses generated under operating current ； A return wire need not be installed only when it causes no interference to adjacent signal lines. Article 10: When single-core cables or phase-separated lead-clad cables are used for three-phase circuits, there shall be no ferromagnetic loops formed by adjacent iron components around each phase. Article 11: The normal operating voltage of a cable circuit should generally not exceed 15% of the cable’s rated voltage. Any increase in the voltage of such a cable circuit must undergo testing, evaluation, and approval by the relevant higher-level authorities. Article 12: At the intermediate and terminal connections of the cable, the cable’s shielding, lead wrapping, and metallic connection boxes must be in good electrical contact with one another so as to be at the same potential. The ends of the cable shall be grounded in accordance with the provisions of the \"Regulations for the Grounding of Substation Equipment\". Section 2: Provisions for Direct Burial of Cables Article 13: Cables that are to be buried directly underground should generally be armored cables. Only short sections of unarmored cables are permitted to be used during cable repairs, but such cables must be provided with mechanical protection. When selecting directly-buried cable routes, attention should be paid to the soil surrounding the cables; it should not contain substances that can corrode the metal coating of the cables (such as strong acid or alkali solutions, lime, slag, humus, and organic waste) ； Attention should also be paid to pest infestations and severe anode areas. Article 14: The burial depth of cables, the clear distance between cables, as well as the clear distance from other pipelines in terms of proximity and intersection, shall comply with the following provisions: 1. The minimum clear distance between cables and the ground as well as buildings ； (1) The burial depth of directly buried cables (from the ground surface to the cable’s outer coating) is 0.7 meters ； (2) 0.6 meters from the cable sheath to the foundation of the underground structure (or as specified by the local urban construction authority, but not less than 0.3 meters). In case of item (1) listed above, where the cable passes through farmland, it may be advisable to deepen it appropriately to prevent damage from agricultural machinery. 2. Minimum clear distance when cables are placed horizontally close to each other: (1) No specification for control cables ； (2) Between power cables, or between them and control cables: 0.1 meters for 10 kV and below, 0.25 meters for above 10 kV ； (3) There should be a 0.5-meter distance between cables (including communication cables) used by different departments. For item (3) listed above, it can be reduced to 0.1 meters if the cable is separated by a partition; no specification applies when it is inserted into a tube. 3. The minimum clear distance between intersecting cables is 0.5 meters. Within one meter before and after the intersection point, the cable should be separated; if a partition is used, this distance can be reduced to 0.25 meters. No specific requirement applies when the cable is placed inside a tube. 4. Minimum clear distance between cables and underground pipelines when they are close to each other or intersect: (1) The clear distance when a cable is close to a thermal pipeline (including oil pipelines) is 2 meters ； (2) The clear distance between the cable and thermal pipelines (including oil pipelines) is 0.5 meters ； (3) The clear distance between the cable and other pipes when they are close to or intersecting each other is 0.5 meters. For the heat pipes specified in items (1) and (2) above, necessary measures shall be taken depending on the site conditions to ensure that the temperature rise of the soil at the location where the cables are buried does not exceed 10 at any time℃ ； If protective measures are in place for item (3) listed above, no requirement is specified for the clear distance. It is prohibited to lay cables parallel above or below the pipes. Article 15: The distance between the cable and the main trunk of a tree should generally be no less than 0.7 meters. If the distance specified above cannot be maintained in certain areas of urban greening, measures can be taken, to be resolved through consultation between the two parties. Article 16: When cables cross urban streets, highways, or railways, they shall be laid in pipes or tunnels. The inner diameter of the tube shall not be less than 1.5 times the outer diameter of the cable, and shall not be less than 100 millimeters. The depth of the pipe crown above the bottom of the railway tracks or road surface should be no less than 1 meter, above the bottom of drainage ditches it should be no less than 0.5 meters, and above the city street surface it should be no less than 0.7 meters ； Apart from spanning the width of roads or railways, the length of the pipe should generally extend 2 meters on each end; on urban streets, it should extend above the road surface. When cables intersect with DC electrified railways, appropriate anti-corrosion measures should be taken. Article 17: When cables are laid along railways, the minimum allowable approach distance shall comply with the following provisions: 1. 3 meters between the cable and the ordinary railway tracks ； 2. No provisions are made for cables and rails in DC electrified railways, but appropriate anti-corrosion measures should be taken (see Chapter 4). Article 18: The potential difference between the cable’s lead sheath and the ground shall not exceed +1 volt. It shall also not exceed the requirements stipulated in the local regulations for preventing electrocorrosion of underground pipelines. Article 19: The stray current density flowing into the soil from the lead sheath of armored cables shall not exceed 1.5 microamperes per square centimeter. Article 20: When cables are laid directly buried, the bottom of the cable trench must have good soil; there should be no stones or other hard debris. Otherwise, a layer of soft soil or filler 100 millimeters thick should be laid. After the cables are laid, they should be covered with a layer of soft soil and sand 100 millimeters thick, followed by a concrete protective plate; the coverage width should extend 50 millimeters on each side beyond the diameter of the cables. However, in cases of necessity, bricks may also be used to replace the concrete protective panels. Article 21: When directly-buried cables are introduced from earth trenches into tunnels, manholes, and buildings, they should be placed inside pipes, with the pipe openings sealed to prevent water leakage. When Cable No. 22 emerges from underground or a cable trench onto the surface, a 2-meter section above the ground shall be protected with a metal pipe or cover, and its root portion shall extend 0.1 meter below the ground surface. Armored cables in power plants and substations may not require protection if there is no risk of mechanical damage ； However, unarmored cables should be protected. Article 23: For cables laid side by side underground, the positions of their joint boxes must be staggered from each other, with a clear distance between them of not less than 0.5 meters. Article 24: The exterior of the cable intermediate joint box shall be equipped with a protective cover to prevent mechanical damage. Plastic cable splices are an exception. Article 25: For cable lines laid in suburban areas and open spaces, signs indicating the location of the cables shall be installed. Section 3: Provisions for the Installation of Cables in Ditches and Tunnels Article 26: Cables laid inside buildings, tunnels, and cable trenches that do not contain sand or soil should be of type with bare armor or a non-flammable outer covering. If a cable line has joints, measures should be taken around those joints to prevent the spread of flames. The fire protection requirements for cable trenches and cable tunnels shall also comply with the relevant provisions of the \"Technical Regulations for the Design of Thermal Power Plants\" and the \"Technical Regulations for the Design of Substations\". Article 27: In tunnels and cable trenches, cables should maintain the minimum allowable distances specified in Table 2 (in millimeters). Table 2: Name, Cable Tunnel, Cable Tray. Height: 1900; no specified value. When there are cable trays on both sides, the horizontal clear distance between the trays (width of the passage): 1000, 500. When there is a cable tray on one side, the horizontal clear distance between the tray and the wall (width of the passage): 900, 450. Vertical clear distance between cable trays on different levels: For power cables of 10 kV and below: 200, 150; for 20 kV or 35 kV cables: 250, 200; for 110 kV and below: not less than 2D① + 50. For control cables: 100, 100. Horizontal clear distance between power cables: 35, 35 (but not less than the outer diameter of the cable). ①D refers to the outer diameter of the cable. Article 28: When cables are fixed to a building and installed horizontally, if the outer diameter of the power cable is greater than 50 millimeters, supports should be installed every 1000 millimeters ； For power cables with an outer diameter of less than 50 millimeters and control cables, supports should be installed every 600 millimeters ； The single-core cables arranged in an equilateral triangle should be secured with straps every 1000 millimeters. When installed vertically, power cables should be secured every 1000 to 1500 millimeters. For cables with a cross-sectional area of 1500 square millimeters or more, when fixing them to a building, due attention must be paid to the mechanical forces resulting from the thermal expansion and contraction of the cables due to changes in load. Fixing methods that are rigid or flexible should be selected in accordance with the principle of uniform stiffness throughout the entire cable circuit. Article 29: Continuous grounding wires shall be installed along the entire length of cable tunnels and trenches, with both ends of these wires connected to the grounding electrodes. The specifications of the grounding wire shall comply with the Technical Code for Grounding Design of Power Equipment. In addition to meeting insulation requirements, the lead sheaths and armoring of cables should all be interconnected with each other as well as connected to the ground wire. Article 30: All metal structures installed outdoors, as well as those placed in manholes, tunnels, and cable trenches, must be fully galvanized or coated with anti-rust paint. Article 31 Cable tunnels and cable trenches shall be equipped with good drainage facilities, and cable tunnels shall also have adequate ventilation facilities. Section 4: Provisions for the Installation of Cables on Bridge Structures Article 32: Cables installed on bridges that are subject to frequent vibrations should be fitted with cushions made of elastic materials (such as sand pillows or elastic rubber). A slack portion for the cable should be left at both ends of the bridge abutments and at the expansion joints. To prevent the cable from being damaged due to structural expansion and contraction. Article 33: Cables installed on wooden bridges shall be placed in iron pipes. When laying cables on bridges with other structures, they should be placed in cable trenches under the walkways or housed in pipes made of fire-resistant materials; however, in areas where no one will come into contact with them, the cables can be laid exposed on the bridge. Article 34: Cables laid exposed to the air should be kept as far as possible from direct sunlight; if necessary, shading covers can be installed. The exposed armor should be coated with asphalt paint to prevent corrosion. Section 5: Provisions for Cable Laying in Trunking Systems Article 35: Cables laid in trunking systems shall be those with reinforced bare lead shielding or plastic sheaths. The conduit should be made of a material that has no chemical effect on the cable’s metal sheath, and its inner surface should be smooth. Article 36: The location and spacing of cables entering the well shall be determined based on the allowable tension during cable installation, as well as factors such as the manufacturing length of the cables and their geographical location. It is generally not advisable to exceed 200 meters. Section 6 Provisions for Laying Cables Underwater Article 37 Cables laid underwater shall be armored with metal wires ； If the tensile force is not high, cables with steel tape armor are permitted to be used ； Under high tensile forces, the cable may twist into loops because the single-layer armor wires tend to lose their torsional strength. Pre-twisted or double-layer metal wire armor with opposite twist directions should be used as much as possible. Article 38: Submarine cables shall be supplied as complete lengths, but flexible joints are permitted. The entire length of the cable should be buried as deep as possible, at least 0.5 meters beneath the riverbed. Article 39: If underwater cables cannot be buried at sufficient depth, measures shall be taken to prevent damage from external forces. And fixed warning signs and riverbank surveillance are installed in accordance with the regulations of the navigation authorities. In rivers with frequent shipping traffic, protective steel cables should be installed as much as possible within the protection zone of the underwater cables. Article 40: When underwater cable lines are laid parallel to each other, the spacing between them should be as follows: 1. If burial is not possible, the spacing should be at least twice the depth of the highest water level ； 2. During burial, it depends on the burial method or the operational capacity of the burial machine. Article 41: When setting the oil pressure in underwater oil-filled cables, in addition to taking into account the changes in oil pressure caused by load variations, it is also necessary to ensure that the oil pressure inside the cable at the deepest point is greater than the water pressure at that location during high water levels, thereby preventing water from entering the cable in case of leaks in the lead coating. Section 7: Other Requirements for Cable Installation Article 42: When laying cables, if the average temperature at the location where the cables are stored within 24 hours prior to laying, as well as the temperature at the laying site, is below the following values, the cables shall be pre-heated: 1. For paper-insulated cables of 35 kV and below, 0°C (for non-dripping cables, in accordance with the manufacturer’s specifications) ； 2. Oil-filled cable, -10℃ ； 3. Rubber-insulated cables, as specified by the manufacturer ； 4. Plastic-insulated cable, 0°C. Article 43: Preheating of cables can be carried out using the following methods: 1. Heating by raising the temperature of the surrounding air: When the temperature is between 5 and 10°C, 72 hours are required ； At a temperature of 25°C, it takes 24 to 36 hours. 2. Heating by passing current through the cable core conductor: The heating current shall not exceed the cable’s rated current. The surface temperature of the cable after heating can be determined based on local climate conditions, but it must not be lower than +5°C. When heating armored cables with single-phase current, a cable core connection method that prevents the formation of induced currents within the armor should be used. The heated cable should be laid as soon as possible; the time it can be left untreated before laying generally should not exceed one hour. When the cable cools below the ambient temperature specified in Article 42, it shall not be bent any further. Article 44: When the ambient temperature is below -10°C, paper-insulated cables are permitted to be installed only in emergency situations, and only if they are heated with electric current both before and during installation. Article 45: Cable splices and ends shall have reliable waterproof seals to prevent moisture from entering. For connectors and terminal blocks lacking operational experience, they should be evaluated through testing, with their use being increased gradually over time. Article 46: The outlet wires of cable terminations shall be kept in a fixed position, and the distance (in millimeters) between their live exposed parts and the grounding part shall not be less than the values specified in Table 3. Article 47: Nameplates indicating the name or number of the circuit, etc., shall be installed on the cables and intermediate connectors in cable trenches, tunnels, and manholes, as well as on the terminal ends at both ends of the cables. After construction or major repairs, it is necessary to verify whether the nameplates attached to both ends of the cable match. The phase color of the cable terminal should be distinct and match the phase of the power system. Table 3 Voltage (kV): 1–3, 6, 10, 20, 35, 110, 220, 330. Inside the house: 75, 100, 125, 180, 300; 850/900. Inside the house: 200, 200, 200, 300, 400; 900/1000, 1800/2000, 2600/2800. Note: For voltages of 110 kV and above, it is a grounded system; in these values, the numerator represents the distance relative to ground, while the denominator represents the distance between phases. Article 48: The personnel responsible for installing cables, connectors, or terminals must be qualified cable technicians who have received specialized training. Article 49: The installation of cable connectors or terminals should be carried out under favorable weather conditions. It is necessary to avoid installation during rainy days, snowy days, or in environments with high temperatures. When installing outdoor connectors or terminals, measures must also be taken to prevent dust and foreign contaminants. Section 8: Cable Spare Parts Article 50: Cables should be stored in a dry place with a covered shelter; pads should be placed under the cable reels to prevent them from sinking into the soil. Cable reels must not be placed horizontally. Article 51 stipulates that for spare parts of oil-filled cables, it is also necessary to regularly check whether the oil pressure is within the specified range and whether there is any oil leakage. Article 52: Cables and accessories at all voltage levels in operation should generally be equipped with spare parts for emergencies, so as to meet the need to replace damaged cables and accessories within a single incident. The quantity of such spare parts should be determined with consideration for cost savings and based on past operational experience. Some spare parts can be centrally stored by designated entities within the cable network. Article 53: Where part of a cable route passes over bridges or ducts, there shall be a section of emergency spares for each such section, whose length shall be sufficient to cover the entire distance across the bridge or duct. Article 54: Due to the difficulties in maintenance and the long repair time required for underwater cables, it is permitted to lay accident standby cables parallel to the main cables in advance. Furthermore, on land in general, a spare cable (or phase) should not be laid in advance. Article 55: Each cable operation department shall formulate management procedures for accident spare parts. The use of accident spare parts shall be carried out in accordance with the management regulations for accident spare parts. Section 9: Technical Documents Article 56: All types of cables must include a cross-sectional view of the cable (refer to Figure 1), indicating the necessary structure and dimensions. Article 57: The operation department of the cable network shall have available for its use: 1. A general topographic map of all the cable lines under its jurisdiction. The scale is generally 1:5000, mainly to indicate the name of the line and its relative position ； 2. System wiring diagram of the cable network ； 3. Protocol file for the cable route path. Article 58: Direct-buried cable lines must have detailed layout drawings (refer to Figure 2); the scale is generally 1:5000, 1:100 (or even higher) in areas with dense underground pipelines, and 1:1000 in areas with sparse pipelines. For cable lines laid in parallel, it is preferable to use a single drawing, but the relative positions of each line must be indicated. And indicate the plan view of underground pipelines. Article 59: Cable lines with hydraulic pressure shall be provided with documents such as the pressure distribution diagram of the oil supply system and the set values for hydraulic pressure, as well as a wiring diagram for alarm signals. Article 60: Cable lines must have records of their original specifications: accurate details regarding length, cross-sectional area, voltage, model, and date of installation; as well as information on the models and numbers of intermediate connectors and terminal fittings, along with the date they were installed (refer to Tables 1 and 2 in Appendix 1). Article 61: Where there are special structures along the cable route, such as bridges, tunnels, manholes, and conduit shafts, drawings of these special structures shall be provided. Article 62: The installation and maintenance of cable joints and terminals shall be carried out in accordance with relevant technical standards and the overall design and assembly drawings ； The general layout must be accompanied by detailed part drawings indicating the materials. Article 63: Cable lines must have operation records, records of accident dates, locations, and causes, as well as records of any changes made to the original equipment (refer to Tables 1 and 2 in Annex 1). Article 64: In the event of an accident or a breakdown during preventive tests on cable lines, it is necessary to keep records of the investigation, including the location, cause, and repair process. Based on these records, plans to prevent similar incidents are formulated, and the investigation records are filed in the operation archives of each line on an annual basis. For matters of unknown cause that require assistance or resolution, they should be accumulated and included as topics for focused research. Article 65: Any changes or modifications to the cable line must be promptly reflected in the corresponding technical documents to maintain their accuracy. Chapter 2: Prevention of Mechanical Damage to Cable Lines Article 66: The cable operation department must be aware of and keep track of all excavation activities along the cable lines, and regularly urge relevant parties to strictly comply with the \"Regulations on the Protection of Power Lines\" or other local regulations regarding the protection of underground pipelines. Cable lines in areas of frequent excavation on the outskirts of the city should be equipped with clear warning signs, and the public should be encouraged to help protect these cables. For underwater cable routes, a protective zone of certain width is designated in accordance with the navigation regulations set by the authorities in charge of the waters; anchoring by ships is prohibited. Depending on the traffic volume of ships, watch posts are installed when necessary, along with facilities designed to attract the attention of ships. Article 67: Cables that become exposed due to excavation must be supervised by cable specialists, and construction workers shall be informed of the precautions related to the work, with written instructions provided. In the protection area of underwater cable lines, in the event of any violations of navigation regulations, the relevant authorities responsible for that water area should be notified so that effective measures can be taken as much as possible, such as stopping underwater operations or dropping anchors, in order to avoid damage caused by accidentally snagging the underwater cables. Article 68: Cables that have been dug out and are completely exposed shall be fitted with protective covers and suspended. The distance between suspensions should not exceed 1.5 meters; single-core cables must not be tied up for suspension using wire ； When suspending multi-core cables with wire, they must be protected by backing plates. Article 69: Excavation work completed