Introduction to Low Voltage Cables

It is a conductor covered with an insulation layer, protective layer, shielding layer, etc., used to transmit power or signal current, signal voltage. According to voltage, it can be divided into high-voltage cables and low-voltage cables. Compared with low-voltage overhead lines and low-voltage overhead insulated lines, low-voltage cable lines have higher costs and are more difficult to lay and maintain. However, due to their reliable operation, no poles, no floor occupation, unobstructed view, and less external influence, they are widely used in low-voltage distribution systems.

structure

It consists of three parts: wire core, insulation layer, and protective layer. The wire core is used for conducting current and is generally made of stranded copper or aluminum wires. There are several types of low-voltage cables, including single core, double core, three core, and four core. Double core cables are used for single-phase circuits, while three core and four core cables are used for three-phase three wire and three-phase four wire circuits, respectively. Single core cables can be applied to single-phase or three-phase circuits as needed. The commonly used cross-sectional areas of low-voltage cable cores include 10, 16, 25, 35, 50, 70, 95120150185240 mm, etc.

characteristic

Low voltage cables have the characteristics of reliable operation, no poles, no floor occupation, unobstructed view, and less external influence, and are widely used in low-voltage distribution systems.

Classified by insulation material

1. Oil immersed paper insulated power cables are power cables that use oil immersed paper as insulation. Its application history is the longest. It is safe and reliable, with a long service life and low price. The main drawback is that the laying is limited by the drop. Since the development of non drip impregnated paper insulation, the problem of drop limitation has been solved, allowing oil impregnated paper insulated cables to continue to be widely used.

2. The insulation layer of plastic insulated power cables is extruded plastic power cables. Commonly used plastics include polyvinyl chloride, polyethylene, and cross-linked polyethylene. Plastic cables have a simple structure, convenient manufacturing and processing, light weight, convenient laying and installation, and are not limited by laying height. Therefore, it is widely used as medium and low voltage cables and has a trend of replacing adhesive impregnated oil-paper cables. Its disadvantage is the presence of dendritic breakdown, which limits its use at higher voltages.

3. The insulation layer of rubber insulated power cables is made of rubber and various additives, which are thoroughly mixed and extruded onto the conductive wire core, and then heated and vulcanized. It is soft and elastic, suitable for occasions with frequent movement and small bending radius during laying.

Commonly used insulation materials include natural rubber styrene butadiene rubber mixture, ethylene propylene rubber, butyl rubber, etc.

Classified by voltage level

1. Low voltage cable: suitable for fixed installation on transmission and distribution lines with AC 50Hz and rated voltage of 3kV and below for power transmission.

2. Medium and low voltage cables: (generally referring to 35KV and below): PVC insulated cables, polyethylene insulated cables, cross-linked polyethylene insulated cables, etc.

3. High voltage cables: (generally 110KV and above): polyethylene cables and cross-linked polyethylene insulated cables, etc.

4. Ultra high voltage cable: (275~800KV).

5. Ultra high voltage cables: (1000KV and above).