Fire risks and prevention measures of wire and cable laying

Fire hazards exist in the power system of electric wire and cable laying in
In the cable manufacturing process, leading to cable insulation electrical insulation performance degradation, destruction, planted fire hazards. The main reason is: the insulation medium containing impurities, moisture and air bubble; insulation thickness; main insulation between the conductor and the shield surface, burr, air gap, resulting in the insulating layer in the uneven distribution of electric field intensity.
Cables and pipelines or cables too close to the long-term over load, high temperature insulation aging caused by spontaneous combustion caused by overheating, short circuit, electrical insulation, breakdown ignition. Cable on cable tray cable bridge because of tension and the phenomenon of thermal expansion and contraction of the edges of the mechanical damage to the cable, the cable failure protection layer and insulating layer, the electric insulation performance.
Cable terminal box fault and spontaneous combustion, because the production process of rough, open the insulator in air exposure time is too long, make the insulation damp, resulting in the explosion in the operation. Cable head surface moisture or dirt, cable head porcelain casing collapse and lead to phase distance is too small will lead to the line of fire.
Cable connector crimping tight, welding is not strong, the oxidation during the operation; injection dose of insulating material, cable joint box does not meet the requirements, or pouring box memory hole; cable box sealing is bad or damaged cracks in moisture, insulation breakdown, fire and explosion.
Cable tunnel debris piled up, cable or cable bracket on the ash too thick, cable tunnel is flammable gas flammable liquid leakage through high temperature or fire ignition cable, fire or explosion occurred.
Now widely used around the bag type insulating material volume resistivity, dielectric coefficient than the cable insulation dielectric coefficient, low volume resistivity. Under strong electric field, the insulation leakage current, dielectric loss of the material will lead to the increase of the heating cable accessories. Coupled with the cable terminal and intermediate joint conductors, is the use of artificial crimp crimping pliers, contact resistance is larger than the resistance of the cable conductor wire core, very difficult to achieve resistance and cable conductor wire core, which will give fire cable, cable is buried hidden trouble.
Oil filled cable laying low and high difference occurred, cable head drip oil or oil leakage, resulting in the loss of insulating oil of high end of the cable, insulation and fire resistance increase coking breakdown.
Human factors, is another important cause of fire accident of wire, cable. For example, operators do not according to the rules and regulations, errors caused by cable, the cable short circuit, overload, wire, cable surface increased exponentially fever, causing electrical fire accidents.
Hazard analysis of electric power system in fire and the cause of wire and cable laying
In high-rise buildings, for wire, cable laying into the beam erection line frame, wire, cable once the fire, the consequences be unbearable to contemplate. Because of using the wire, cable insulation layer are flammable rubber, polyvinyl chloride and hydrogen molecular organic compounds, produced in the burning heat of 19000 ~ 46000kJ/kg. The melting point of copper wire, cable at about 1038 DEG C, the melting point of 658 degrees in the aluminum core wire, cable insulation layer, and the melting point is far lower than these values, such as polyvinyl chloride plastic melting temperature is only 120 degrees. When the group of bundles of wires, cables, hot melt accident temperature of 800 ~ 1100 DEG C, the threat of high-rise buildings is particularly important, smoke in the accident, it is difficult to observe the source of fire, accident treatment is very difficult. The tragic fire in recent years, Sichuan Department store, Hongkong Kowloon Building, no one is not caused by a wire, cable.
Electric fire accident will cause the other chain accident. Generally speaking, plastic wire, cable not only fire spread speed, but also produce large amounts of toxic and harmful gas, such as hydrogen chloride, carbon monoxide poisoning, suffocation, make the person is in danger of death. At the same time, when in the off gas after combustion reaction of halides will generate strong acid, made of " two pollution; ", the modern intelligent high electrical, electronic equipment subjected to acid erosion, the consequences are quite serious.
There is a fire hazard of power system electrical wire and cable laying in preventive measures
We should pay attention to from the thought, the strict all aspects of design, manufacturing, installation, maintenance, maintenance, implementation of the whole process of management, improve the safety and reliability of cable. Design and selection of electric wire and cable, to be exact. In the construction of high-rise building wire, cable to disposal technique. Between buildings, between layer and layer, layer and layer, frame and wall, elevator shaft and frame and control room will be strict with fireproof blocking material, thoughtful and sealed, so the wire, cable fire flames will not on others. Special wire, cable laying frame bundle group, to show the trend, on the electrical bridge box, box, joint box settlement severe closed in case of fire, right after the accident spread.
To keep cable away from fire and heat source. In the laying of cables, cable pipe should as far as possible from the steam and oil pipeline, keep a safe distance between them. Flammable gas or flammable liquid pipe trench, should not laying cable. If the pipe trench in thermal insulation, to take measures to protect the cable should not be in place, the cable overhead explosion or fire hazard.
Prone to or contributed to the spread of fire site protection in the fire, to isolate the flammable and explosive materials in the laying of cables in cable section, vulnerable to external influence, to fire processing necessary. In order to effectively prevent the fire from spreading to expand, reduce the loss of the fire, set the firewall and fire in the cable trench, cable tunnel and other parts, the fire control in the cable section, in order to reduce the scope for cable trench near the fire, oil filled electrical equipment should be sealed well, through the hole in the wall of holes and shafts to all cable the control room of the mezzanine floor, cable out of the perforation, must be in the refractory tight sealing, fire resistance limit shall not be less than 1h, in order to prevent the cable fire disaster spread to non fire.
In different plant or workshop at the junction, outdoor enter indoor, power distribution room busbar at different voltage, power distribution equipment, at the junction of different units and the main transformer cable connections, long distance cable at intervals of 100m, both the firewall and fire resistance period; in the tunnel and the main control, centralized control, network control room the connection is provided with a door, firewall, fire, fire doors can be automatically or manually close the distance; tunnel in the wall, should also be fireproof door lock.
To set the alarm and automatic fire extinguishing device. For initial fire fighting cable, cable interlayer, a proper position in the cable tunnel set up automatic alarm and fire fighting equipment, in order to put the cable initial fire nipped in the bud.
In order to reduce cable fire hazards, in the design, construction, operation 3 aspects should pay attention, take effective measures. All the relevant units, to clear the cable fire prevention responsibility system, regularly organize personnel to inspect the cable fire prevention measures. In short, as long as make every attempt, to minimize the possibility of fire retardant cable and the cable fire accident, can effectively control.