The difference between power cable and ordinary wire is mainly cable size and complicated structure. The cable is mainly composed of the following four parts. Conductor: made of high conductivity material. Insulation: insulation materials used for cables should have high insulation resistance, high breakdown electric field strength, low dielectric loss and low dielectric constant. Seal sheath: protect insulated wire from mechanical, moisture, moisture, chemicals, light and other damage. For easy insulation, lead or aluminum extrusion seal is generally used. Protective covering: to protect the seal sheath from mechanical damage. Generally, galvanized steel strip, steel wire or copper strip, copper wire, etc. are used as armor sheaths outside the sheath (known as armored cable), and the armor layer also ACTS as an electric field shielding and prevents external electromagnetic interference. In order to avoid the corrosion of the steel band and steel wire by the surrounding medium, they are coated with asphalt or wrapped around the jute layer or extruded polyethylene and PVC sleeve.
In addition to the above differences, cable has obvious advantages. Compared with the overhead lines, cable is the line insulation distance is small, the advantages of small occupation space, underground installation and not more than take up little space, is not affected by the environment pollution, high transmission reliability, less interference to the personal safety and the surrounding environment. As a result, cables are often used in densely populated areas and congested areas with heavy traffic. It is of great importance to the modernization construction.