Six reasons for the problems of wire and cable
1. Insulation aging and deterioration
The insulation of wires and cables is subject to the thermal, chemical and mechanical effects brought by the electric action, so that the insulating medium undergoes physical and chemical changes, which reduces the insulating ability of the medium. The insulation is damp, the intermediate joints or terminal heads are damped due to the sealing of the structure up and down or the installation quality is not good.
2. Cable overheating
There are many reasons for cables to overheat. The internal cause is the local heating caused by the free air gap inside the cable insulation, thereby carbonizing the insulation. The external cause is that cables installed in cable-intensive areas, cable tunnels, etc., cables passing in drying pipes, and cables close to pipes will accelerate insulation damage due to cable overload or poor heat dissipation.
3. Mechanical damage
Mainly refers to the cable damage caused by external force. This is mainly due to mechanical action such as vehicle vibration, which deforms the cable. Deformation of the cable leads to excessive bending, which damages the inner insulation or causes air gaps within the insulation.
4. Corrosion of protective layer
Due to electrolysis or chemical action, the lead package of the cable is corroded. Due to the different nature and degree of corrosion, the lead package has red, yellow, orange and light yellow compounds or pores similar to sponges.
5. Overvoltage causes breakdown
Atmospheric overvoltage and internal overvoltage cause the cable insulation to exceed the allowable stress and cause breakdown. Moreover, analysis of actual problems shows that many outdoor termination problems are caused by atmospheric overvoltage.
6. Design and manufacturing process problems of intermediate joints and terminal heads
When the semiconductor is peeled off, the inner insulation is damaged or there are particles, dust and other impurities on the insulation surface; the cable head is poorly sealed, so that there is moisture inside the insulation, resulting in the insulation being damp; the cable joint process is not standard, the sealing is not standardized, resulting in grounding; the production environment humidity is too high , causing the insulation integrity of the production part (cable head) to be damp; the cable grounding error, causing the ground wire to form a loop or break.