1, external damage. According to the analysis of operation in recent years, a lot of cable faults are caused by mechanical damage especially in Shanghai Pudong in the rapid economic development.
2, insulation damp. This situation is also very common, usually occurs in the buried or pipe cable connector. For example: unqualified cable connectors and connectors in humid climates will make the connector into the water or mixed with water vapor for a long time to form water branches under the electric field, and gradually damage the dielectric strength of the cable and cause failure.
3, chemical corrosion. Cable buried directly in the role of acid and alkali areas, often result in cable sheathing, lead or outer sheath corrosion, protective layer due to long-term chemical corrosion or electrolytic corrosion, resulting in protective layer failure, insulation will also lead to Cable fault. The unit: the cable corrosion situation is quite serious
4, long-term overload operation. Due to the thermal effect of the current, the load current will inevitably lead to the heating of the conductor when it passes through the cable. At the same time, the skin effect of the charge and the eddy current loss of the steel armor will also generate additional heat, which will increase the temperature of the cable.
5, cable connector failure. Cable connector is the weakest link in the cable line, the direct fault of personnel (poor construction) caused by the cable connector failure often occur. During the process of making a cable connector, the construction personnel may cause the insulation of the cable head to be lowered if there is a problem that the connector is not crimped tightly and the heating is insufficient, which may cause an accident.