When the cable fault tester is in use, the problem is often detected and analyzed as follows:
1) External force damage. Judging from the operation analysis in recent years, especially in Pudong, Shanghai, where the economy is developing rapidly, a considerable number of cable failures are now caused by mechanical damage. For example, non-standard construction during cable laying and installation can easily cause mechanical damage; civil construction on directly buried cables can also easily damage cables in operation. Sometimes if the damage is not serious, it will take months or even years for the damaged part to be completely broken down to form a fault, and sometimes a short-circuit fault may occur if the damage is serious, which directly affects the safety production of the electricity user.
2) The insulation is damp. This situation is also very common, and generally occurs at the cable joints in direct burial or piping. For example: unqualified cable joints and joints made in humid weather conditions will cause the joints to enter water or water vapor. For a long time, water branches will be formed under the action of the electric field, which will gradually damage the insulation strength of the cable and cause failure.
3) Chemical corrosion. The cable is directly buried in the area with acid and alkali, which will often cause the cable armor, lead skin or outer sheath to be corroded. The protective layer suffers from chemical corrosion or electrolytic corrosion for a long time, resulting in the failure of the protective layer and the reduction of insulation. The cable is faulty. Chemical: the unit’s cable corrosion situation is quite serious
4) Long-term overload operation. Overload operation, due to the thermal effect of the current, the conductor heating will inevitably be caused when the load current passes through the cable. At the same time, the skin effect of the charge, the eddy current loss of the steel armor, and the insulation loss will also generate additional heat, which will increase the temperature of the cable. During long-term overload operation, the excessively high temperature will accelerate the aging of the insulation, and even the insulation will be broken down. Especially in the hot summer, the temperature rise of the cable often leads to the first breakdown of the weak insulation of the cable, so in the summer, there are more cable faults.
5) The cable connector is faulty. Cable joints are the weakest link in the cable line, and cable joint failures caused by direct faults (poor construction) by personnel often occur. In the process of making cable joints, if there are original nets such as insufficient joint crimping, insufficient heating, etc., the insulation of the cable head will be reduced, which will cause an accident.
6) Environment and temperature. The external environment and heat source of the cable can also cause the cable to overheat, insulation breakdown, and even explosion and fire.
7) The normal aging of the cable body or other reasons such as natural disasters.