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What is the relationship between the cable rated voltage and the number of cable cores?
What is the relationship between the cable rated voltage and the number of cable cores? Do you understand? The following will give you a detailed introduction to the selection conditions of multicore cable types.
1. Selection conditions for 1~5 core cables of 1kV and below.
Single core cable
To avoid or reduce intermediate joints when the circuit is longer, the working current is larger or the circuit is laid underwater, or the single-core cable has better comprehensive technology and economy than the multi-core cable, single-core cable can be used.
Low-voltage DC power supply loop, single-core cable can be used when needed.
2-core cable
When the neutral point of the power supply of 1kV and below is directly grounded, the number of cores of the single-phase circuit cable. When the protection line and the neutral line share the same conductor, a 2-core cable should be used.
For DC power supply loop, 2-core cable should be used.
3-core cable
When the neutral point of the power supply of 1kV and below is directly grounded, the number of cores of the single-phase circuit is: when the protection line and the neutral line are independent, a 3-core cable should be used.
4-core cable
For 4-core cables (3+1 cables) of 1kV and below, the 4th core of them is not only used as a protective ground, but also conveys unbalanced current and short-circuit current in the power system. Its size is determined by unbalanced current and short-circuit current, but generally it should not be less than 1/2 of the phase line.
For three-phase four-wire low-voltage power distribution systems of 1kV and below, when the protection line and the neutral line share the same conductor, a 4-core cable should be used instead of a 3-core cable plus a single-core cable to form a loop, or even directly Use the metal sheath or armor layer of the 3-core cable as the neutral wire. Otherwise, when the 3-phase current is unbalanced, it is equivalent to the operating state of a single-core cable, which is likely to cause power frequency interference.
5-core cable
Three-phase four-wire low-voltage power distribution systems of 1kV and below, some electrical equipment distribution lines with high safety requirements, and some communication centers and automation equipment that need to ensure electrical safety and anti-interference grounding should be used The 5-core TN-C low-voltage power distribution system makes the protection line (PE line) and the neutral line (PN line) independent of each other. The cross-sectional area of the cable core is generally 3 large 2 small or 4 large 1 small or 5 large.
2.Second, the choice of the number of cores in the medium and high voltage cables
For the selection of the number of cores of the 3~35kV three-phase power supply loop cable When circuits with larger working currents or cables are laid underwater, 3 single-core cables can be used for each circuit; in addition to the above cases, 3-core cables should be used, and 3-core cables can be used for general package type or 3 Single-core cable stranded structure type.
For the 110kV three-phase power supply circuit, 3 single-core cables can be used for each circuit, except for laying in lakes, under the sea and other places and the cable section is not large.
For three-phase power supply circuits above 110kV, 3 single-core cables should be used 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 used each time.
Single-core cables should be used for HVDC transmission systems; coaxial 2-core cables can also be used when laying underwater in lakes, seas, etc.
Qingdao Hold one Cable Co., Ltd. is located in the beautiful Qingdao, with more than 200 sets (sets) of advanced production and testing equipment, and the process equipment has reached the domestic leading level. At present, the company’s products have been widely used in electricity, energy, transportation, chemical, steel And other national key industries, and exported to more than a dozen countries such as Africa and Southeast Asia.
The company's leading products:
1. Wires and cables: overhead conductors of 750kV and below, 10～500kV cross-linked cables, plastic cables of 1kV and below, cables for electrical equipment, etc.;
2. Insulated bus: 1-35kV composite shielded insulated bus;
3. Special cables: fire-resistant cables, high-temperature (flame-retardant) cables, computer cables and instrument cables, photovoltaic cables, automotive cables, drag chain cables, elevator cables, robot cables, trolley cables, wind power cables, etc.;
4. Polymer materials: cross-linked polyethylene insulating material, PE sheath material, PVC sheath material