The selection of XLPE insulated power cables should follow the following principles: the rated voltage should be greater than or equal to the voltage at the installation point.
1. Short-circuit fault caused by insulation damage
The protective layer of the cable will be damaged during the laying process, or the insulation layer of the cable will be damaged by mechanical damage during the operation, resulting in interphase or damage to the protective layer of the cable, and the arc will cause the protection of the insulating material and the outer layer of the cable. The layer material burns and catches fire.
2. Long-term overload operation of the cable
Long-term overload operation, the working temperature of the cable insulation material exceeds the higher allowable temperature of normal heating, thereby accelerating the insulation aging of the cable. This insulation aging phenomenon usually occurs in the entire cable line. Due to the aging of the cable insulation layer, the insulation material will lose or reduce the insulation layer and mechanical properties, so it is easy to break and catch fire, and even burn in many places along the entire length of the cable.
3. Insulation breakdown of the intermediate junction box
The intermediate joint of cable joint box is oxidized, heated and gummed during operation due to loose crimping, weak welding or improper joint material selection; When making the cable intermediate joint, the quality of insulating agent poured into the intermediate joint box does not meet the requirements. When pouring the insulating agent, there are air holes in the box and the cable box is poorly sealed and damaged, which causes moisture leakage. The above factors can cause insulation breakdown, form short circuit, and cause cable explosion and fire.
4.Cable head burning
Because the surface of the cable head is contaminated by moisture, the porcelain sleeve of the power cable head will break, and the distance between the wires will be too small, which will cause arcing and fire, which will cause the cable head and the surface of the cable to be insulated. The insulation of the outlet is burning.
5. Cable fire caused by external fire and heat source
For example, the spread of fire in the fuel system, the explosion of the fuel circuit breaker, the spontaneous combustion of pulverized coal in the boiler crushing system or coal conveying system, the baking of high-temperature steam pipes, the chemical corrosion of acid and alkali, welding sparks, etc. may cause the cable to catch fire.