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What Is The Relationship Between The Rated Voltage Of The Cable And The Number Of Cable Cores?
- Jun 25, 2018 -

What is the relationship between the rated voltage of the cable and the number of cable cores? Do you understand it? The following small series will introduce the details of cable core selection conditions.


电缆额定电压与电缆芯数之间有什么关系?


What is the relationship between the rated voltage of the cable and the number of cable cores?

What is the relationship between the rated voltage of the cable and the number of cable cores? Do you understand it? The following small series will introduce the details of cable core selection conditions.


I. 1kV and below selection conditions for 1~5 core cables


Single core cable


When the circuit is long, the circuit with large operating current or underwater is laid, in order to avoid or reduce the intermediate connector, or if the single core cable has a better comprehensive technical economy than the multi-core cable, a single-core cable may be used.


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


2-core cable


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


DC power supply circuit should adopt 2-core cable.


3-core cable


When the neutral point of 1kV and below are directly earthed, the number of single-phase circuit cable cores is: When the protection line and the neutral line are independent, a 3-core cable should be used.


4-core cable


For 4-kV and below 4-core cables (3+1 cable), the 4th core of the 4-core cable not only serves as a protective ground, but also carries unbalanced current and short-circuit current in the power system. Its size is determined by the unbalanced current and the short-circuit current, but it must not be less than 1/2 of the phase line.


For 1kV and below three-phase four-wire low-voltage distribution systems, when the same conductor is used for the protection line and the neutral line, a 4-core cable should be used instead of using a 3-core cable and a single-core cable to form a circuit, or even directly Use a 3-wire cable with a metal sheath or armored layer as the neutral wire. Otherwise, when the three-phase current is unbalanced, it is equivalent to the operating state of the single-core cable, which easily causes power frequency interference.


5-core cable


For 1kV and below three-phase four-wire low-voltage distribution systems, some safety-critical electrical distribution lines, and some communication centers and automation equipment that both ensure electrical safety and ground against interference should be used. The 5-core TN-C low-voltage power distribution system makes the protection line (PE line) and neutral line (PN line) independent, and the cable core area is generally 3 large and 2 small or 4 large, 1 small or 5 large.


Second, the choice of high voltage cable core number


For the selection of 3~35kV three-phase power supply circuit cores. When a circuit or cable with a large operating current is laid underwater, three single-core cables can be selected for each circuit. In addition to the above cases, a three-core cable should be used. A three-core cable can be used as an ordinary turn-on type, and can also be used as an option. Single core cable twisted construction type.


For the 110kV three-phase power supply circuit, three cores can be used in addition to the lake, seawater, etc., where the cable cross-section is not large, and three single-core cables can be used for each loop.


For three-phase power supply loops above 110kV, three single-core cables should be used for each loop.


Electrified railways and other high-voltage AC single-phase power supply circuits should use two-core cables or two single-core cables for each selection.


For HVDC transmission systems, single-core cables should be used; when laying underwater in lakes and seas, coaxial 2-core cables can also be used.