Causes of folding aging
1. External damage. According to the operation analysis in recent years, especially in the rapidly developing Shanghai Pudong, quite a lot of cable faults are caused by mechanical damage.
2. Damp insulation. This is also common, usually at the end of a cable in a buried or drain pipe. For example: cable joints made unqualified and in humid climate conditions to do the joint, will make the joint water or mixed with water vapor, long time R under the action of the electric field to form water branches, gradually damage the cable insulation strength and cause failure.
3. Chemical corrosion. Cables buried directly in areas with acid and alkali effects will often cause corrosion of the cable armor, lead or outer sheath. Long-term chemical or electrolytic corrosion of the protective layer will lead to failure of the protective layer and reduced insulation, and also lead to cable faults. Change: the cable corrosion situation of unit is quite serious
4. Long-term over-load operation. In overload operation, due to the thermal effect of current, the conductor will inevitably heat up when the load current passes through the cable. Meanwhile, the skin effect of charge, the eddy current loss of steel armor and the insulation medium loss will also generate additional heat, which will increase the temperature of the cable.
5. Cable joint failure. The cable joint is the weakest link in the cable line. The fault of the cable joint caused by the personnel's direct fault (poor construction) often occurs. In the process of making the cable connector, if the connector is not pressed tightly and the heating is not sufficient, etc., the insulation of the cable head will be reduced, thus causing an accident.
6. Environment and temperature. The external environment and heat source in which the cable is located will also cause the cable temperature to be too high, the insulation to break down, and even the explosion and fire.