Structure classification of power cables
The basic structure of the power cable is composed of four parts, which are the wire core (conductor), the insulation layer, the shield layer and the protective layer.
(1) wire core
The wire core is the conductive part of the power cable, which is used to transport the electric power and is the main part of the power cable.
The insulation layer is an indispensable component of the electric cable structure, which is separated from the core of the wire and the earth and the different phases of the earth, and is electrically isolated from each other.
(3) shielding layer
15KV and above electric power cable generally should have the conductor shield layer and the insulation shield layer.
(4) protective layer
The protective layer is a protective layer to protect the power cable from the external impurities and moisture intrusion, as well as to prevent direct damage to the external power cable.
By voltage level:
According to the voltage level, it can be divided into medium and low voltage power cables (35 thousand volts and below), high voltage cables (more than 110 thousand volts), ultra high voltage cables (275 to 800 thousand volts) and extra high voltage cables (1 million volts and above). In addition, the current system can be divided into AC and DC cables.
According to the insulation material:
1, oil impregnated paper insulated power cables is insulated with oil paper. Its application history is the longest. It is safe, reliable, long service life and low price. The main disadvantage is that the laying of the gap limit. Since the development of a drop of tidewater dip paper insulated, it solves the gap restrictions and oil impregnated paper insulated cables can continue to be widely used.
2, plastic insulated power cable insulation is insulated with the extrusion of plastic. Commonly used plastics are polyvinyl chloride, polyethylene, crosslinked polyethylene. The plastic cable has the advantages of simple structure, convenient manufacture and processing, light weight, convenient laying and installation, and is not limited by the height of the laying. It is widely used for medium voltage cables, and tends to replace the sticky impregnated oil paper cable. The biggest shortage is the presence of a branch breakdown phenomenon, which limits its use in higher voltage.
3, rubber insulated power cable is insulated with rubber and a variety of coordination agent. It is produced by full mixing in the conductive wire extrusion bag and then heating and curing. It is soft and flexible, and is suitable for the occasions of frequent movement and small bending radius.
Commonly used as insulation are natural rubber compound insulation - SBR mixtures, ethylene propylene rubber, butyl rubber etc..