3.2　Number of Power Cable Cores

3.2.1　Where the neutral of power sporce of 1kV or below is solidly grounded，the number of cable cores for the three-phase circuit shall be determined in accordance with the following requirements:

1　Where the protective wire is grounded by connecting with the exposed conductive parts of energized equipment，the following requirements shall be met:

1）If the protective wire and the neutral line share the same conductor，four-core cables shall be used.

2）If the protective wire is independent of the neutral line，five-core cables should be used；however，four-core cables together with an additional protective conductor may be used provided that the requirements of Article 5.1.16 of this code are met.

2　Where the earth of exposed conductive parts of energized equipment is independent of that of the power supply system，four-core cables shall be used.

3.2.2　Where the neutral of power supplies of 1kV or below is solidly grounded，the number of cable cores for single-phase circuits shall be selected in accordance with the following requirements:

1　Where the protective wire is grounded by connecting with the exposed conductive parts of energized equipment，the following requirements shall be met:

1）If the protective wire and the neutral line share the same conductor，two-core cables shall be used.

2）If the protective wire is independent of the neutral line，three-core cables should be used；however，two-core cables together with an additional protective conductor may be used provided that the requirements of Article 5.1.16 of this code are met.

2　Where the earth of exposed conductive parts of energized equipment is independent of that of the power supply system，two-core cables shall be used.

3.2.3　The number of cable cores for 3-35kV three-phase power supply circuits shall be selected according to the following requirements:

1　For circuits with a large working current or cables laid underwater，three single-core cables may be used for each circuit.

2　In other cases，three-core cables of ordinary belted type shall be used，or alternatively，three single-core cables in stranded configuration may be used.

3.2.4　For 110kV three-phase power supply circuits，three single-core cables may be used for each circuit，except for cables laid underwater in lakes or seas and with small cable cross sections，in which case three single-core cables may be used.

For three-phase power supply circuits of 110kV or above，three single-core cables shall be used for each circuit.

3.2.5　For HV AC single-phase power supply circuits such as that for electric railways，two-core cables or two single-core cables shall be used for each circuit.

3.2.6　The number of cable cores for DC power supply circuits shall be selected according to the following requirements:

1　For LV DC power supply circuits，two-core cables should be used，and single-core cables may be used as an alternative.

2　For HV DC transmission systems，single-core should be used，and coaxial two-core cables may be used when laid underwater in lakes and seas.