The most direct cause of aging failure of wire and cable

The most direct cause of aging failures of wire and cable is breakdown and breakdown.

There are many factors that lead to the reduction of insulation. According to actual operating experience, the following situations can be summed up.

(1) External damage. From the analysis of operations in recent years, especially in cities with rapid economic development, a considerable number of cable faults are now caused by mechanical damage. For example, when the cable is laid and installed, the construction is not standardized and it is easy to cause mechanical damage. It is also very easy to damage the cable during operation by carrying out the civil works on the buried cable. Sometimes if the damage is not serious, it will take several months or even several years to cause complete breakdown of the damaged part to form a fault, and sometimes severe damage may lead to a short-circuit fault, which directly affects the safe production of power plants and power-using units.

(2) Insulation is damp. This situation is also very common, usually occurs in the cable joints in the direct burial or exhaust pipe. For example: The unqualified cable joints and the joints under humid weather conditions will cause the joints to intrude or mix in water vapor. After a long time, they form water branches under the effect of the electric field and gradually damage the insulation strength of the cables and cause failures.

(3) Chemical corrosion. Cables buried directly in areas with acid and alkali effects often cause cable sheathing, lead sleeves, or outer jackets to be corroded. The protective layer is subject to long-term chemical or electrolytic corrosion, resulting in failure of the protective layer and reduced insulation. For cable failures, the corrosion of cables in chemical units is quite serious.

(4) Long-term overload operation. Overload operation, due to the thermal effect of the current, the load current through the cable will inevitably lead to conductor heating, and the skin effect of the charge and the eddy current loss of the steel file, insulation dielectric loss will also generate additional heat, so that the cable temperature increases. During long-term overload operation, an excessively high temperature will accelerate the aging of the insulation so that the insulation is broken down. Especially in the hot summer season, the temperature rise of the cable often leads to the first breakdown of the weak cable insulation. Therefore, in the summer, the cable fault is particularly high.

(5) Cable connector failure. Cable joints are the weakest link in the cable route. Faults of cable joints caused by direct personnel faults (bad construction) occur frequently. During the process of making cable joints, the construction personnel will cause the insulation of the cable head to be reduced if the joints are not tightly pressed and the heating is insufficient, which may cause accidents.

(6) Cable aging causes: environment and temperature. The external environment and heat source of the cable can also cause the cable temperature to be too high, insulation breakdown, and even explosion.