1. Temperature of wire and cable:
The electrical conductivity of metals decreases with the increase of temperature. When the temperature is not very high (close to the melting point) or very low (close to absolute zero), the resistivity and temperature have the following linear relationship: ρ{{0}}ρ01 plus (T -T0).
2. Impurities in wire and cable materials:
Metals contain certain impurities that will increase their resistance. The influence of impurities on metal resistance, the analysis depends on the type, content of impurities, and the state of impurities in the metal, aluminum, antimony, arsenic, phosphorus, nickel, lead, etc. are harmful impurities of copper, when the arsenic content is 0.35 percent When , the resistivity of copper will increase by 50 percent ; the main harmful impurities in aluminum conductors are silicon and iron.
3. Plastic cold deformation of wire and cable:
It is reminded that the elastic deformation of the wire and cable has little effect on the metal resistance, while the plastic deformation increases the resistance. When the cold working deformation exceeds 10 percent , the resistance increases significantly. For pure metals, the increase in resistance due to cold deformation is generally not more than 4 percent . The electrical resistivity of the electric round aluminum rod is 0.02801 before drawing. After drawing, it is produced into the electrical round aluminum wire of the required specifications, and the resistivity is 0.028264.
4. Heat treatment (annealing):
After the metal is cold-deformed, due to the change of metal crystallization, the tensile strength, yield strength and elasticity increase, while the conductivity and elongation decrease. Under toughening, to achieve the purpose of improving elongation and conductivity, the resistance can be restored to the level before deformation.
5. Environment for wire and cable use:
When environmental factors cause pollution or oxide layer on the metal surface, as well as moisture and oil stains, the resistance of the metal will increase. The thickness of the cladding layer is obtained by calculation. Copper has the effect of promoting aging for some impregnating agents (such as mineral oil, rosin compound impregnating agent, etc.) and vulcanized rubber. In this case, tin can be plated on the surface of the copper wire so that the copper does not directly contact the insulating layer.
The above is the relevant knowledge about the electrical conductivity of wires and cables, you can simply understand. Targeted attention during construction or after installation can ensure the highest possible performance of the cable. When the conductor temperature exceeds the allowable working temperature of the insulating material, the aging of the insulating material will be accelerated, and the insulation will be softened and deformed first at the bend of the cable, resulting in the inability to meet the needs of the cable.
