The most direct reason for the failure of wire and cable is the decrease of electrical and mechanical properties. There are many factors, according to the actual operating experience, wire and cable summed up the following situations.
1 reasons for the aging of the cable: insulation damp, usually occurs in the buried or row of cable joints. For example: the production of cable joint failure and do joint in humid climates, will make joint water or mixed with water vapor, a long time in the electric field forming water treeing, gradually damage the cable insulation performance caused by fault.
2) cable aging causes: chemical corrosion, direct buried cable in acid-base interaction area, often caused by armored cable or outer protective layer of corrosion protection layer, due to prolonged exposure to chemical or electrolytic corrosion, resulting in the failure of protective layer, thereby affecting the insulation performance, will also lead to cable fault.
3) cable aging reasons: long-term overload operation, due to the thermal effect of the current, the current through the cable conductor and cause fever, skin effect and eddy current loss, charge the dielectric loss of steel armor will produce additional heat, so that the cable temperature. Long term overload operation, too high temperature will accelerate the aging of insulation, as well as insulation breakdown. Especially in the hot summer, the temperature rise of the cable often leads to the breakdown of the cable insulation is the first breakdown, so in the summer, the cable fault is particularly high.
4 cable aging reasons: the environment and temperature, the external environment and the heat source of the cable will also cause the cable temperature is too high, insulation breakdown, and even the explosion of fire.