What are the functions of power cables and the requirements for their materials?
(1) the basic structure of power cable. The power cable is mainly composed of four parts: core (also called conductor), insulation layer, shielding layer and protective layer.
(2) the role of each part and the requirements for the use of materials:
The core is the conductive part of the cable, which is used to transmit electric energy, and is the main part of the cable.
The requirements for wire core materials are good electrical conductivity, good mechanical properties and abundant resources.
The insulation layer separates the core from the earth and the core with different phases on the electrical side to ensure the transmission of electric energy. The requirements for insulating material are high pressure resistance, low dielectric loss, good corona resistance, stable chemical properties, low temperature resistance, good heat resistance, good mechanical processing performance, long service life and cheap price.
6kV and above cables usually have conductor shielding and insulation shielding.
The function of the shielding layer is to eliminate the unsmoothness of the surface of the conductor (the tip produced by the multi wire twisted pair), which causes the increase of the electric field intensity on the surface of the conductor, so that the insulating layer and the cable conductor are in contact with the conductor effectively.
In order to better contact the insulation layer and the metal coat, the outer shielding layer is usually covered on the outer surface of the insulation layer.
Requirements for shielding material:
The conductor shielding material of oil paper cable is usually metallized tape or semi conductive tape. The insulating shield generally uses a semi conductive paper tape.
Plastic or rubber insulated conductors or insulated shielding materials are semi conductive plastic and semi conductive rubber respectively.
Plastic and rubber cables without metal sheathed are shielded copper or copper wires outside the insulation shield.
The protective layer is to protect the cables from external impurities and water intrusion and prevent external forces from damaging the cables directly. The requirement for the protective layer material is that the sealing material and corrosion resistance of the protective layer material must be good and have certain mechanical strength.
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