Selection of power cable cross-section

1、 Principles for selecting the cross-section of power cable conductors:

1. The temperature of the cable conductor under the action of working current shall not exceed the allowable value of the cable's service life. The working temperature of the cable conductor in the continuous working circuit should comply with the regulations.

2. The temperature of the cable conductor under the action of short-circuit current and short-circuit time shall comply with the provisions in the table above.

3. The voltage drop of the connected circuit under the action of working current shall not exceed the allowable value of the circuit.

4. In addition to meeting the requirements of clauses 1-3 above, the cross-section of 10kV and below power cables should also be selected based on the comprehensive economic principles of the initial investment and operating costs during the service life of the cable.

2、 Selection of cable conductor cross-section

The general steps for cable design and selection are to first determine the cable model based on the laying conditions. The selection of cable conductor cross-section should be combined with the local laying environment. For cables of 66kV and above, the current industry standard for cable current carrying capacity calculation JB/T 10181 should be referred to. The commonly used cables of 35kV and below can be calculated based on the current carrying capacity provided by the manufacturer and the local installation environment according to the correction factor.

The cable cross-section should meet the requirements of continuous allowable current, short-circuit thermal stability, and allowable voltage drop. Verify the voltage drop of cables with voltage levels of 10kV and below, because voltage verification is only carried out when the voltage is below 6 or 10kV and the wire cross-section is below 70-95mm2. For wires with a cross-section greater than 70-95mm2, increasing the cross-section does not have a significant effect on reducing voltage loss, and it will cause an increase in investment and non-ferrous metals. For example, using electrostatic capacitors for compensation or transformers with load voltage regulation and other measures are appropriate, but technical and economic comparisons should be made to determine. Verify the thermal stability of cables of 10kV and above during short circuits.