CAUSE OF CABLE FIRE AND EXPLOSION

Cause of cable fire and explosion

1. The cable head burns

Because the surface of the cable head is damp and dirty, the ceramic sleeve of the cable head is broken and the distance between the lead wires is too small, which leads to flashover and fire, causing the surface insulation of the cable head and the insulation of the lead wires to burn.

2. Short circuit fault caused by edge damage

The protective lead sheet of the power cable is damaged during laying or the cable insulation is mechanically damaged during operation, which causes the insulation breakdown between the cable phases or between the lead sheets, and the resulting arc causes the insulating material and the outer protective layer of the cable to burn and catch fire.

3. The cable is overloaded for a long time

During long-term overload operation, the operating temperature of the cable insulation material exceeds the maximum allowable temperature for normal heating, causing the cable insulation to age and dry up. This phenomenon of aging and dry insulation usually occurs on the entire cable line. Due to the aging and drying of the cable insulation, the insulating material loses or reduces the insulating properties and mechanical properties, so it is prone to strike through fire and even burn at multiple places along the entire length of the cable.

4. Fire source and heat source lead to cable fire

Such as the spread of fire in the oil system, the spread of the explosion and fire of the oil circuit breaker, the spontaneous combustion of pulverized coal in the boiler pulverizing system or the coal conveying system, the baking of the high temperature steam pipeline, the chemical corrosion of acid and alkali, welding sparks and other fires, all of which can cause the cable fire.

5. The immersed cable runs and leaks due to the height difference

When the oil-immersed cable is laid with a large height difference, the phenomenon of oil dripping from the cable may occur. As a result of the flow, the upper part of the cable is dried up due to the loss of oil, the thermal resistance of this part of the cable increases, and the paper insulation cokes and breaks down in advance. In addition, because the oil in the upper part runs down, it makes room at the upper cable head and creates a negative pressure, which makes the cable easy to absorb moisture and make the end wet. 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. Wet cables and oil leaks increase the chance of failure and fire.

6. Insulation breakdown of indirect joint box

The intermediate joint of the cable joint box is oxidized, heated, and glued during operation due to insufficient crimping, weak welding or improper selection of joint materials; 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 or damaged and leaks into the moisture. The above factors can cause insulation breakdown, form a short circuit, and cause the cable to explode and catch fire.

What to do when the cable explodes

(1) Cut off the power supply of the fire cable. If the cable catches fire, no matter what the cause is, the power supply should be cut off immediately. Then, according to the path and characteristics of the cable, carefully check to find out the fault point of the cable, and at the same time, personnel should be quickly organized to fight.

(2) Cut off the power supply of the non-faulty cable in case of fire in the cable trench. When the cables in the cable trench catch fire, if the cables laid side by side in the same trench have obvious possibility of fire, the power supply of these cables should be cut off. If the cables are arranged in layers, first cut off the power supply of the heated cable above the fire cable, then cut off the power supply of the cable side by side with the fire cable, and finally cut off the power supply of the cable below the fire cable.

(3) Close the fire door of the cable trench or block both ends of the cable trench. When the cable in the cable trench catches fire, in order to avoid air circulation and to quickly extinguish the fire, the fire door of the cable trench should be closed or both ends should be blocked, and the fire should be extinguished by suffocation.

(4) Do a good job of personal protection when putting out cable fires. Since the fire of the cable will produce a lot of smoke and poisonous gas, the rescue personnel should wear a gas mask when putting out the fire of the cable. In order to prevent personal electric shock during the rescue process, the rescuers should also wear rubber gloves and insulating boots. If one phase of the high-voltage cable is found to be grounded, the rescuers should observe: Do not enter indoors within 4m from the fault point, and do not enter outdoors from the fault. Points within 8m, so as not to step voltage and contact voltage hurt people. Rescue of injured personnel is not limited to this limit, but protective measures should be taken.

(5) Fire-fighting equipment used to extinguish cable fires. Fire extinguishers should be used to extinguish cable fires, such as dry powder fire extinguishers, “1211″ fire extinguishers, carbon dioxide fire extinguishers, etc.; dry sand or loess can also be used to cover; if water is used to extinguish fire, it is best to use water spray; Other methods may be used to put out the fire. After the power supply is cut off, water can be poured into the cable trench, and the fault can be sealed and extinguished with water.

(6) When fighting a cable fire, it is forbidden to directly touch the steel armor of the cable and the moving cable with your hands.