Analysis of the Causes of Power Cable Fires

First, the insulation layer of the power cable is composed of various combustible materials such as paper, oil, hemp, rubber, plastic, asphalt, etc. 

Therefore, the cable has the possibility of fire and explosion. 

The cause of the cable fire and explosion is:

●Short circuit failure caused by insulation damage. 

The protective lead of the power cable is damaged during laying or the cable insulation is mechanically damaged during operation, causing insulation breakdown between the cables or between the lead, and the resulting arc causes the insulating material and the outer protective layer material to ignite.

●The cable is overloaded for a long time. 

For a long period of overload operation, the operating temperature of the cable insulation material exceeds the maximum allowable temperature of normal heating, so the insulation of the cable is aging and dry. 

This phenomenon of aging of the insulation usually occurs on the entire cable line. 

Due to the aging of the cable insulation, the insulation material loses or reduces the insulation performance and mechanical properties, so it is easy to burn by fire, and even the combustion and fire occur simultaneously along the entire length of the cable.

●The oil-immersed cable is smashed and leaked due to the height difference. 

When the height difference of the oil-immersed cable is large, cable squeezing may occur. 

As a result of the turbulence, the upper part of the cable is dried up due to the loss of oil, and the thermal resistance of the part of the cable is increased, causing the paper insulation to be cooked and broken down in advance. 

In addition, since the upper oil is squatting down, a space is made at the upper cable head and negative pressure is generated so that the cable is easy to absorb moisture and the end is damp. 

The lower part of the cable generates a large static pressure due to the accumulation of oil, which causes the cable head to leak oil. 

Cable dampness and oil leakage increase the probability of a malfunctioning fire.

● Insulation breakdown of the intermediate connector box. 

The intermediate joint of the cable joint box is not tightly crimped, the welding is not tight, or the joint material is improperly selected. 

The joint is oxidized, heated, and flowed during operation; when the intermediate joint of the cable is made, the quality of the insulating agent poured into the intermediate joint box does not match. 

It is required that when the insulating agent is poured, the air hole in the box and the cable box are poorly sealed and damaged, and the moisture leaks into the box. 

The above factors can cause insulation breakdown and short circuits, causing the cable to explode and ignite.

●Cable head burning. 

Due to the moisture accumulation on the surface of the cable head, the cable sleeve of the cable head is broken and the distance between the lead wires is too small, causing flashover and ignition, causing insulation of the surface of the cable head and insulation of the lead wire.

●External fire and heat sources cause cable fires. 

Such as oil system fire spread, oil circuit breaker explosion fire spread, boiler powder system or coal handling system coal powder spontaneous combustion, high-temperature steam pipe baking, acid, and alkali chemical corrosion, welding sparks, and other fires can make cables a fire has occurred.