1. Insulation damage causes short circuit fault
The protective lead cover of power cables is damaged during laying or the cable insulation is damaged by mechanical damage in operation, which causes the insulation breakdown between cables or between the lead cover. The electric arc will cause the insulation materials and the protective layer of cables to burn up.
2. The cable is overloaded for a long time
For a long time in overload operation, the operating temperature of the cable insulation material exceeds the maximum allowable temperature of normal heating, making the cable insulation aging and dry up. This phenomenon of aging and dry up insulation usually occurs in the whole cable line. As the cable insulation ages and dries up, the insulation material loses or reduces the insulation performance and mechanical properties, so it is easy to break down and burn, or even burn up in many places along the whole length of the cable.
3. Insulation breakdown of intermediate connector box
The intermediate joints of the cable connector box are oxidized, heated and glued during operation due to loose pressing, weak welding or improper selection of joint materials; When making cable intermediate joint, the quality of insulating agent in the intermediate joint box does not meet the requirements. During the filling of insulating agent, there will be air holes in the box memory and leakage of moisture into the cable box due to poor sealing and damage. All the above factors can cause insulation breakdown, form short circuit, and cause cable explosion and fire.
4. Cable end combustion
As the surface of the cable head is contaminated by moisture, the porcelain bushing of the cable head is broken and the distance between the lead wires is too small, which leads to flashier fire and causes the surface insulation of the cable head and lead wire insulation to burn.
5. Cable fire caused by external fire source and heat source
Such as oil system fire spread, oil circuit breaker explosion fire spread, boiler pulverized coal system or coal conveying system coal spontaneous combustion, high temperature steam pipeline baking, acid and alkali chemical corrosion, welding spark and other fire, can cause the cable fire.