Factors of fire and explosion of power cable and how to save fire

(1) Insulation damage causes a short-circuit fault. The protection of the power cable is damaged during laying or lead to mechanical damage to the cable during operation, causing insulation breakdown between the cables or between the lead wires. The resulting arc causes the insulating material and the outer protective layer of the cable to ignite and catch fire.

(2) 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 for normal heating, so that the insulation of the cable is aged and dried up. Such insulation aging and dryness usually occurs on the entire cable line. As the cable insulation is aged and dry, the insulating material loses or reduces the insulation performance and the mechanical performance, so that it is easy to strike fire and burn even at the same time along the entire length of the cable.

(3) The oil-immersed cable is damaged due to height difference and leaks oil. When the height difference of the oil-immersed cable laying is large, the phenomenon of oil slick in the cable may occur. As a result of the turbulent flow, the upper part of the cable is dried up due to the loss of oil, and the thermal resistance of this part of the cable increases, causing coking of the paper insulation and premature breakdown. In addition, since the upper portion of the oil squats downward, a space is created at the upper cable end and a negative pressure is generated, so that the cable easily absorbs moisture and damps the end portions. The lower part of the cable generates a large static pressure due to the accumulation of oil, causing the cable head to leak oil. Cable moisture and oil leaks increase the chance of a fire.

(4) Insulation breakdown of the middle connector box. The middle joint of the cable splice box is not tightly pressed, the welding is not firm or the joint material is not properly selected. During operation, the joint is oxidized, generates heat, and flows. When the cable middle joint is made, the quality of the insulating agent poured in the middle joint box does not meet the requirements. Requirements, when the insulating agent is poured, there are pores in the box and the cable box is poorly sealed, damaged and leaks moisture. All of the above factors can cause insulation breakdown and short circuit, causing the cable to explode and catch fire. Electric Automation Technology Network

(5) The cable end burns. As the surface of the cable head is damped and accumulated, the porcelain casing of the cable head is broken and the distance between the lead wires is too small, causing the flashover to ignite and causing insulation on the surface of the cable head and insulation burning of the lead wire.

(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 fires, the spontaneous combustion of coal powder in coal-fired boiler systems or coal-fired systems, the baking of high-temperature steam pipes, the chemical corrosion of acids and alkalis, the welding sparks, and other types of fire, all of which can make cables Fire.

Extinguishing method

Cable fire fighting method

Once the cable catches fire, it should be extinguished by the following methods:

(1) Cut off the power of the fired cable. When a cable catches fire, it should be cut off immediately regardless of the cause. Then, according to the path and characteristics of the cable, it is carefully checked to find out the point of failure of the cable. At the same time, personnel should be organized to save.

(2) Cut off the non-faulty cable power in the cable trench. When the cables in the cable trenches start to burn, if the cables laid side by side with the same trench have obvious fire potential, the power of these cables should be cut off. If the cable is arranged in layers, first cut off the heat-receiving cable power above the fire-retardant cable, and then cut off the cable power supply that is in parallel with the fire-cable cable, and finally cut off the cable power supply under the fire-breathing cable.

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

(4) Good personal protection when fighting a cable fire. Because the fire of the cable will generate a lot of smoke and gas, fire fighting personnel should wear a gas mask when the cable fire is extinguished. In order to prevent people from getting an electric shock during the rescue process, the rescue personnel should also wear rubber gloves and put on insulated boots. If high-voltage cables are found to be grounded in one phase, the fire-fighting personnel shall observe: Indoors shall not enter within 4m from the point of failure, and outdoor access shall not be allowed. Point within 8m so as not to hurt people by step voltage and contact voltage. The ambulance personnel are not limited to this, but protective measures should be taken.

(5) Fight fire extinguishing equipment used in cable fires. Fire extinguishers should be used to extinguish cable fires, such as dry powder fire extinguishers, “1211” fire extinguishers, and carbon dioxide extinguishers; dry sand or loess can also be used; if water is used for extinguishing fires, spray guns are preferred; if the fire is violent, it is not Other methods may be adopted The insulation layer of the power cable is composed of various combustible materials such as paper, oil, hemp, rubber, plastics, and asphalt. Therefore, the cable may have the possibility of fire and explosion. The cause of the cable explosion is:

(1) Insulation damage causes a short-circuit fault. The protection of the power cable is damaged during laying or lead to mechanical damage to the cable during operation, causing insulation breakdown between the cables or between the lead wires. The resulting arc causes the insulating material and the outer protective layer of the cable to ignite and catch fire.

(2) 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 for normal heating, so that the insulation of the cable is aged and dried up. Such insulation aging and dryness usually occurs on the entire cable line. As the cable insulation is aged and dry, the insulating material loses or reduces the insulation performance and the mechanical performance, so that it is easy to strike fire and burn even at the same time along the entire length of the cable.

(3) The oil-immersed cable is damaged or leaks due to height difference. When the height difference of the oil-immersed cable laying is large, the phenomenon of oil slick in the cable may occur. As a result of the turbulent flow, the upper part of the cable is dried up due to the loss of oil. This part of the cable has increased thermal resistance, causing coking of the paper insulation and premature breakdown. In addition, since the upper portion of the oil squats downward, a space is created at the upper cable end and a negative pressure is generated, so that the cable easily absorbs moisture and damps the end portions. The lower part of the cable generates a large static pressure due to the accumulation of oil, causing the cable head to leak oil. Cable moisture and oil leaks increase the chance of a fire.

(4) Insulation breakdown of the middle connector box. The middle joint of the cable splice box is not tightly pressed, the welding is not firm or the joint material is not properly selected. During operation, the joint is oxidized, generates heat, and flows. When the cable middle joint is made, the quality of the insulating agent poured in the middle joint box does not meet the requirements. Requirements, when the insulating agent is poured, there are pores in the box and the cable box is poorly sealed, damaged and leaks moisture. All of the above factors can cause insulation breakdown and short circuit, causing the cable to explode and catch fire. Electric Automation Technology Network

(5) The cable end burns. As the surface of the cable head is damped and accumulated, the porcelain casing of the cable head is broken and the distance between the lead wires is too small, causing the flashover to ignite and causing insulation on the surface of the cable head and insulation combustion of the lead wire.

(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 fires, the spontaneous combustion of coal powder in coal-fired boiler systems or coal-fired systems, the baking of high-temperature steam pipes, the chemical corrosion of acids and alkalis, the welding sparks, and other types of fire, all of which can make cables Fire.

Extinguishing method

Cable fire fighting method

Once the cable catches fire, it should be extinguished by the following methods:

(1) Cut off the power of the fired cable. When a cable catches fire, it should be cut off immediately regardless of the cause. Then, according to the path and characteristics of the cable, it is carefully checked to find out the point of failure of the cable. At the same time, personnel should be organized to save.

(2) Cut off the non-faulty cable power in the cable trench. When the cables in the cable trenches start to burn, if the cables laid side by side with the same trench have obvious fire potential, the power of these cables should be cut off. If the cable is arranged in layers, first cut off the heat-receiving cable power above the fire-retardant cable, and then cut off the cable power supply that is in parallel with the fire-cable cable, and finally cut off the cable power supply under the fire-breathing cable.

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

(4) Good personal protection when fighting a cable fire. Because the fire of the cable will generate a lot of smoke and gas, fire fighting personnel should wear a gas mask when the cable fire is extinguished. In order to prevent people from getting an electric shock during the rescue process, the rescue personnel should also wear rubber gloves and put on insulated boots. If high-voltage cables are found to be grounded in one phase, the fire-fighting personnel shall observe: Indoors shall not enter within 4m from the point of failure, and outdoor access shall not be allowed. Point within 8m so as not to hurt people by step voltage and contact voltage. The ambulance personnel are not limited to this, but protective measures should be taken.

(5) Fight fire extinguishing equipment used in cable fires. Fire extinguishers should be used to extinguish cable fires, such as dry powder fire extinguishers, “1211” fire extinguishers, and carbon dioxide extinguishers; dry sand or loess can also be used; if water is used for extinguishing fires, spray guns are preferred; if the fire is violent, it is not Other methods may be used to save the fire. After the power is cut off, water can be poured into the cable trench to seal the fault with water and extinguish the fire.

(6) When fighting a cable fire, do not touch the cable reel or move the cable by hand. To save, after the power is cut off, water can be poured into the cable trench to seal the fault with water and extinguish the fire.