The principle of power cable mainly involves the transmission and distribution of electric energy, which is transmitted to the destination through the conductor. Power cable consists of conductor, insulation layer and protective layer. The conductor is generally made of metal materials with good conductivity such as copper and aluminum, the insulation layer is made of insulating materials such as polyethylene and cross-linked polyethylene, and the protective layer protects the cable from mechanical damage and environmental corrosion.
Power cable has a long history of use. Since the American inventor T.A. Edison invented the first cable in 1879, power cable technology has been continuously developing. In 1889, the British S.Z. Ferranti laid a 10 kV oil-impregnated paper insulated cable between London and Deptford, which marked the application of power cable technology in practice.
The working principle of power cable is based on the phenomenon of electromagnetic induction, that is, when a part of the conductor in a closed circuit cuts the magnetic flux line in a magnetic field, a current will be generated in the conductor. This principle is the basis of equipment such as distribution transformers in modern power systems3.
As a special type of cable, the working principle of coaxial cable involves the formation of a current loop. Coaxial cable is divided into four layers from the inside to the outside: the center copper wire (single-strand solid wire or multi-strand twisted wire), plastic insulator, mesh conductive layer and wire sheath. The center copper wire and the mesh conductive layer form a current loop for conducting alternating current. The design of coaxial cable solves the problem that ordinary wires are equivalent to an antenna emitting radio when transmitting high-frequency current. The radio emitted by the center wire is isolated by the mesh conductive layer, and the emitted radio is controlled by grounding to ensure the transmission efficiency of the signal4.
In summary, the principle of power cable not only involves the basic concepts of transmission and distribution of electric energy, but also includes the application of electromagnetic induction phenomenon and the working principle of special cables such as coaxial cable.