GB 50217-2018 Standard for design of cables of electric power engineering
1 General provisions
1.0.1 This standard is formulated with a view to making the design of electric power engineering cable be technically advanced, economical and reasonable, safe and applicable, and easy for installation and maintenance.
1.0.2 This standard is applicable to the selection and laying design of power cables and control cables rated 500kV and below in newly built, renovated or expanded power projects for power generation, power transmission and transformation, and power distribution, etc.
It does not apply to the following environments: underground mines; environments for the manufacture, application or storage of gunpowder, explosive and initiating explosive, and production of fuse and initiating explosive device, etc.; water, land and air transportation facilities; nuclear islands in nuclear power plants.
1.0.3 In addition to this standard, the design of electric power engineering cable shall also comply with those stipulated in the current relevant standards of the nation.
2 Terms
2.0.1 flame retardant cables
cables with specified flame retardant properties such as flame retardant characteristics, smoke density, smoke toxicity, and corrosion resistance
2.0.2 fire resistive cables
cables with specified fire resistive properties such as line integrity, smoke density, smoke toxicity, and corrosion resistance
2.0.3 metallic-plastic composite water barrier
a water barrier formed by putting thin metal (such as aluminum or lead foil) sheath in the special composite tape in the plastic layer and enveloped along the longitudinal direction of the cable
2.0.4 thermal resistance
physical quantity defined by Omron rule of the one-dimensional heat dissipation process for the calculation of the cable ampacity by heat network analysis method
2.0.5 auxiliary ground wire
wire configured in parallel to high voltage AC single-core power cable line and earthed at both ends to make induced current form a circuit
2.0.6 direct burying
the laying method that cable is laid into the underground trench and covered with a cushion layer on the bottom of the trench and a covering layer on the cable, and a protective plate is added to bury to the floor
2.0.7 channel
covered channel-type structure without brackets and capable of accommodating a small number of cables
2.0.8 manhole
covered pit-type cable building dedicated to the installation of accessories such as cable connectors or required for pulling cables
2.0.9 cable building
a general term for structures such as cable trench, channel, rack pipe, tunnel, interlayer, vertical (oblique) well, and manhole for laying of cable or placement of accessories
2.0.10 slip fixing
a fixing method that allows the cable to expand and contract with thermal expansion at an axial angle along the fixed place or have lateral movement slightly
2.0.11 rigid fixing
a clamping and fixing method that prevents the cable from being displaced by thermal expansion and contraction
2.0.12 snaking of cable
a laying method for cable in the shape of a snake by which the axial thermal stress of the cable is reduced according to the quantitative parameter requirements, or the amount of free expansion and contraction would be increased
3 Selection of cable type and cross-section
3.1 Materials of power cable conductor
3.1.1 Copper conductors shall be adopted for power cables used in the following cases:
1 motor excitation, important power supply and mobile electrical equipment, etc. need to maintain connecting to a circuit with high reliability;
2 vibration place and working environments exposed to explosion hazard or corrosion to aluminum;
3 fire resistive cables;
4 arranged close to high-temperature equipment;
5 assembly occupancies;
6 conventional island and production-related ancillary facility in nuclear power plant;
3.1.2 Except for products with only copper conductors and copper conductors shall be adopted according to 3.1.1, cable conductors may be copper conductors, aluminum or aluminum alloy conductors. Aluminum alloy conductor should not be selected for the cable with voltage grade of 1kV and above.
3.1.3 The structure and performance parameters of cable conductor shall be in accordance with requirements of GB/T 3953 Round copper wire for electrical purposes, GB/T 3955 Round aluminium wire for electrical purposes, GB/T 3956 Conductors of insulated cables and GB/T 30552 Aluminium alloy wires for conductors of insulated cables, etc.
3.2 Power cable insulation level
3.2.1 The interphase rated voltage of power cable conductor in AC system shall not be less than the voltage of operating line of the circuit used.
3.2.2 The selection of rated voltage between the power cable conductor and insulation shield or metallic sheath in AC system shall meet the following requirements:
1 the neutral point is directly earthed or passes through the low-resistance earthing system. When the earthing protection action removes fault in no more than 1min, the voltage shall not be lower than 100% of the working phase voltage of the circuit used;
1 General provisions
2 Terms
3 Selection of cable type and cross-section
3.1 Materials of power cable conductor
3.2 Power cable insulation level
3.3 Type of power cable insulation
3.4 Type of external sheath of power cable
3.5 Number of power cable cores
3.6 Cross-section of power cable conductor
3.7 Control cable and metallic shielding
4 Selection and configuration for cable accessories and accessory devices
4.1 General requirements
4.2 Oil supply system of self-contained oil-filled cable
5 Cable laying
5.1 General requirements
5.2 Selection of laying methods
5.3 Directly burying of cable
5.4 Laying of cable protection pipe
5.5 Cable laying in cable trench
5.6 Cable laying in cable tunnel
5.7 Cable laying in cable mezzanine
5.8 Cable laying in cable shaft
5.9 Cable laying in other utilities
5.10 Underwater cable laying
6 Cable supports and fixings
6.1 General requirements
6.2 Cable supports and trays
7 Fire prevention and retardation of cables
Annex A Maximum allowable temperature of common power cable conductor
Annex B Selection methods and density curves for economic current cross-section of power cable rated 10kV and below
Annex C Allowable 100% continuous ampacity of common power cable rated 10kV and below
Annex D Correction factors of allowable continuous ampacity of cable under different laying conditions
Annex E Method for calculation of allowable minimum cross-section of cable conductors based on the short-circuit thermal stability conditions
Annex F Calculation methods of normal induced potential of metallic sheath of single-core cable of AC system
Annex G Additional length of cable rated 35kV and below during laying measurement
Annex H Calculation methods for maximum allowable length of pipes in case of putting cables through pipes
Explanation of wording in this standard
List of normative references
