Causes of cable explosion and fire

The insulating layer of the power cable is composed of various combustible substances such as paper, oil, hemp, rubber, plastic, asphalt, etc. Therefore, the cable has the possibility of fire and explosion. The reasons for the fire and explosion of the cable are:

(1) Insulation damage causes short circuit fault. The protective lead skin of the power cable is damaged during laying or the cable insulation is mechanically damaged during operation, causing insulation breakdown between the phases of the cable or between the lead skins, and the resulting arc causes the insulation material and the outer protective layer material of the cable to burn and catch fire.

(2) The cable is overloaded for a long time. Long-term overload operation, the operating temperature of the cable insulation material exceeds the maximum allowable temperature of normal heating, making the cable insulation aging and drying. This phenomenon of insulation aging and drying usually occurs on the entire cable line. Due to the aging and drying of the cable insulation, the insulating material loses or reduces the insulation and mechanical properties, so it is easy to break down and burn, and even burn at multiple places along the entire length of the cable at the same time.

(3) Oil-immersed cables drip and leak oil due to height difference. When the oil-immersed cable is laid with a large height difference, the phenomenon of cable oil dripping may occur. As a result of dripping, the upper part of the cable dries up due to the loss of oil, the thermal resistance of this part of the cable increases, and the paper insulation is coked and broken down in advance. In addition, since the oil in the upper part drips down, there is a space at the upper cable head and negative pressure is generated, so that the cable is easy to absorb moisture and make the end wet. The lower part of the cable generates a lot of static pressure due to the accumulation of oil, causing the cable head to leak oil. Cable damp and oil leakage have increased the probability of failure and fire.

(4) Insulation breakdown of the intermediate joint box. The intermediate joint of the cable joint box is not tightly crimped, welded firmly or the joint material is improperly selected, and the joint is oxidized, heated, and glued during operation; when making the intermediate joint of the cable, the quality of the insulating agent poured into the intermediate joint box does not meet the requirements. It is required that when the insulating agent is poured, there are air holes in the box and the cable box is poorly sealed and damaged, and moisture leaks in. The above factors can cause insulation breakdown, form a short circuit, and cause the cable to explode and catch fire. Electrical Automation Technology Network

(5) The cable head is burning. Due to the moisture accumulation on the surface of the cable head, the cracking of the ceramic sleeve of the cable head and the too small distance between the lead wires lead to flashover and fire, causing the surface insulation of the cable head and the insulation of the lead wires to burn.

(6) External fire and heat sources cause cable fires. Such as the spread of fire in the oil system, the spread of oil circuit breaker explosion fire, the spontaneous combustion of pulverized coal in the boiler pulverizing system or coal conveying system, the baking of high-temperature steam pipes, the chemical corrosion of acid and alkali, electric welding sparks and other fires, can cause the cable to Create a fire.