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What are the principles in selecting the number of cable cores?

Update:28-12-2020
Summary:

A cable is made of one or more mutually insulated condu […]

A cable is made of one or more mutually insulated conductors and an outer insulating protective layer, which transmits electricity or information from one place to another. Everything in the world has its own characteristics and levels. What's more, wire and cable products are widely used and have a wide variety. Even if you are in the industry, it is not exhaustive. Let us take a look at the principle of choosing the number of cable cores.
1. When the neutral point of 1kV and the following power supply is immediately grounded, when the maintenance line and the neutral line in the three-phase control loop share the same electrical conductor, a four-core cable should be used; when the maintenance line and the neutral line are separate, it should be used Five-core cable. When the grounding device of the exposed conductive position of the power receiving equipment and the power system software grounding device are separate, a four-core cable should be used.
2. When the neutral point of 1kV and the following power supply is immediately grounded, when the maintenance line and the neutral line in the single-phase electric control loop share the same electrical conductor, a two-core cable should be used; when the maintenance line and the neutral line are separate, it is appropriate Use a three-core cable. When the grounding device of the exposed conductive position of the power receiving equipment and the power system software grounding device are separate, a two-core cable should be used.
3. In the control loop of 3~35kV three-phase power supply system, when the control loop or cable with large current in operation is laid under water, 3 single-core cables can be used each time; except for the above-mentioned cases, three-core cables should be used. Cable: The three-core cable can adopt the general package type, or the three-core single-core cable twisted wire structure.
4. For the control loop of the AC single-phase power supply system with high voltage communication such as electrified railways, two-core cables or two single-core cables should be used each time.
5. For the control loop of the bottom voltage DC power supply system, two-core cables should be used; single-core cables can also be used. The software of the HVDC power transmission system should adopt a single-core cable; when laying on the bottom of lakes, seas, etc., two-core cables with the same axis can also be used.
6. In the control loop of the 110kV three-phase power supply system, in addition to laying in lakes, under the sea and other places and the cable cross-section is not large, the three-core type can be used, and 3 single-core cables can be used each time. The control loop of the three-phase power supply system around 110kV uses 3 single-core cables for each response.

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