1. Mechanical damage
Cable failures caused by mechanical damage account for a large proportion of cable accidents. The cable is damaged during installation. Excessive mechanical traction will strain the cable and excessive bending will damage the cable; Direct damage caused by external forces and damage caused by natural phenomena (such as vehicle rolling, falling rocks, environmental corrosion, etc.) are easy to cause cable body failure.
2. Wet insulation
The main reason is that the installation technology of intermediate connector and terminal connector is poor, which leads to sealing failure, moisture intrusion and insulation damage.
3. Insulation deterioration
The internal air gap of the cable insulation medium is released under the action of the electric field, thereby reducing the insulation; Overheating can also cause deterioration of the insulation and lead to a reduction in insulation.
4. Overvoltage
The influence of over-voltage, switching over-voltage and fault transient over-voltage will cause cable insulation layer to break and form faults.
5. Poor design and manufacturing process
The moistureproof of intermediate joints and terminal joints, imperfect electric field distribution design, improper selection of materials, poor production process, and non-compliance with operating regulations will all lead to cable head insulation failure.
6. Major defects
The insulating layer material of the cable itself is defective; In the process of wrapping the insulating layer, defects such as wrinkles, cracks, cracks and overlapping gaps will appear on the insulating layer. Defects in the manufacturing of cable joint accessories, nonconformity or unsealing during assembly; Poor maintenance and management of insulating materials lead to moisture, dust and aging of cable insulation.