The cause for aging of wire and cable

1. External force injury. From the analysis of operation in recent years, especially in Shanghai Pudong, where economic development is developing rapidly, quite a lot of cable failures are caused by mechanical damage.

2, the insulation is dampened. This is also a common occurrence, usually in the cable joints where burying or draining pipes are located. For example, the disqualification of the cable joint and the joint under the humid climate will make the joint enter into the water or mix the water vapor. The water branch is formed under the action of the electric field for a long time R, and it will gradually damage the insulation strength of the cable and cause the failure.

3. Chemical corrosion. The cable is directly buried in the area with acid and alkali, which often causes the armour of the cable, the lead skin or the outer protective layer to be corroded. The protective layer has been corroded by chemical or electrolytic corrosion for a long time, resulting in the failure of the protective layer and the decrease of the insulation, and the cable failure. Change: the corrosion of the unit cable is quite serious

4. Long term overloading operation. Over load operation, due to the thermal effect of current, the load current is bound to cause heat of the conductor 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 armour and the loss of the insulating medium will produce additional heat at first, which makes the cable temperature rise.

5. Failure of cable joint. The cable connector is the weakest link in the cable line, and the cable joint fault often caused by personnel direct fault (poor construction) occurs frequently. In the process of making cable joint, if the joint is not tight and the heating is not enough, the insulation of the cable head will be reduced and the accident can be caused.

6. Environment and temperature. The external environment and heat source of the cable will also cause high cable temperature, insulation breakdown and even explosion.