1kV and below for 1 to 5 core cable selection conditions

A, single-core cable

When the line is longer and the working current is larger in the loop or underwater laying, in order to avoid or reduce the intermediate joint, or when the single-core cable has a better comprehensive technical economy than the multi-core cable, the single-core cable can be selected.

Low voltage DC power supply circuit, single-core cable can be used when necessary.

Two, 2-core cable

When the neutral point of the power supply is directly grounded at 1kV and below, the number of cable cores of the single-phase circuit, when the protection line and the neutral line share the same conductor, the 2-core cable should be used.

2-core cables are recommended for the DC power supply circuit.

Three, 3-core cable

When the neutral point of the power supply is directly grounded at 1kV or below, the number of cable cores for the single-phase circuit is as follows: When the protection line and neutral line are independent, a 3-core cable is recommended.

Four, 4 core cable

1kV and below 4-core cable (3+1 cable), of which the fourth core in addition to the protective grounding, but also to transport the power system in the imbalance current and short circuit current. Its size is determined by the unbalance current and short circuit current, but generally not less than 1/2 of the phase line.

1kV and below three-phase four-wire low-voltage distribution system, when the protection line and neutral line use the same conductor, should use 4-core cable, and should not use 3-core cable and single-core cable combination into a primary way, or even directly use the metal sheath or armor layer of 3-core cable as a neutral line. Otherwise, when the 3-phase current is unbalanced, it is equivalent to the operating state of the single-core cable, which is easy to cause power frequency interference.

Five, 5 core cable

1kV and below three-phase four-wire low-voltage distribution system, some electrical device distribution lines with higher safety requirements, as well as some communication and automation equipment that both ensure electrical safety and anti-interference grounding, it is advisable to use 5-core wire TN-C low-voltage distribution system, so that the protection line (PE line) and neutral line (PN line) are independent. The cross-sectional area of the cable core is generally 3 large, 2 small or 4 large, 1 small or 5 large.

Six, the selection of the number of high voltage cable cores

For 3~35kV three-phase power supply circuit cable core selection. When the circuit with large working current or the cable is laid underwater, 3 single-core cables can be selected for each circuit;

In addition to the above cases, 3-core cables should be selected, and the 3-core cables can be ordinary turnkey type or three single-core cables can be twisted.

For the 110kV three-phase power supply circuit, in addition to laying in the lake, sea water and other places and the cable section is not large can choose 3 core, each circuit can choose 3 single-core cables.

For the three-phase power supply circuit above 110kV, three single-core cables should be selected for each circuit.

For high-voltage AC single-phase power supply circuits such as electrified railways, 2-core cables or 2 single-core cables should be selected each time.

HVDC transmission system, should choose a single core cable; When laying in lake, sea and other underwater, coaxial 2-core cable can also be selected.

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