Cable rated voltage and the relationship between the number of cores
In the choice of cable, you need to consider the cable voltage and
cable core number of these two factors, but many people do not understand, here to give you a detailed description of the cable rated voltage and cable core what is the relationship between.
1kV and below the 1-5 core cable selection conditions
Single-core cable
When the circuit is longer and the working current is larger, the single-core cable may be used to avoid or reduce the middle connector or the single-core cable has a better comprehensive technical economy than the multi-core cable. Low-voltage DC power supply circuit, when needed, the single-core cable can be used.
2-core cable
When the neutral point of 1kV and below is directly grounded, the number of cores in the single-phase loop shall be 2-core cable when the same conductor is used for the protection and neutral lines. DC power supply circuit should use 2-core cable.
3-core cable
When the neutral point of 1kV and below is directly grounded, the number of cores in the single-phase loop is: When the protection line and the neutral line are independent, the 3-core cable should be adopted.
4-core cable
A 4-core cable (3 + 1 cable) at 1kV and below, with the 4th core in addition to its protective ground, will also carry unbalanced and short-circuit currents in the power system. Its size is determined by the unbalanced 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 power distribution system, when the protection of the line and the neutral conductor with the same conductor, the 4-core cable should be used instead of using 3-core cable plus a single cable combination of a loop, or even direct The use of 3-core cable metal sheath or armored layer for neutral line mode. Otherwise, when the 3-phase current is unbalanced, it is equivalent to the running status of single-core cable, which will easily cause interference with power frequency.
5-core cable
1kV and below three-phase four-wire low-voltage power distribution system, some of the higher safety requirements of electrical installations distribution lines, and some not only to ensure electrical safety but also anti-interference grounding communication center and automation equipment, should be used 5-wire TN-C low-voltage distribution system, the protection line (PE line) and the neutral line (PN line) are independent, cable core cross-sectional area is generally 3 large 2 small or 4 large 1 small or 5 large.
Medium and high voltage cable core number of choices
For 3-35kV three-phase supply circuit cable core number of choices. When the working current larger circuit or cable laid under water, each circuit can be used three single-core cables; In addition to the above circumstances, the use of 3-core cable should be used, 3-core cable optional common package type, can also be used 3 Root single core cable stranded configuration.
On the 110kV three-phase power supply circuit, in addition to laying in the lake, seawater and other places and the cable cross-section can be used less 3 core, each circuit can be used three single-core cables.
More than 110kV three-phase power supply circuit, each circuit should be used three single-core cables.
Electrified railway high-voltage AC single-phase power supply circuit, should use 2-core cable or each selection of two single-core cables.
HVDC transmission system should use single-core cable; laying in the lake, sea and another underwater, but also the choice of coaxial 2-core cable.
Through the above introduction, we have a relationship between the rated voltage of the cable and the number of cable core has been understanding it, I hope to be helpful to everyone, if there are cable problems, please click consult us!
