Popularize electric power cable fire hazard and cause

　　Power lines and cables are an important part of the power industry and are increasingly used in the development of the national economy. With the development of power industry, supply enterprises is increasing, and large-scale modern factory, the urban construction of high-rise, the popularity of household appliances of urban city appearance, environmental protection, and special safety requirements, make the application of the power cable is becoming more and more widely, but according to the survey data show that the fault caused by the wire, cable itself and external fire ignition cable fire and spread the fire caused by accounting for 40% of the electrical fire, and such a huge fire loss. Therefore, it is extremely important for the mass of consumers to spread the danger of power lines and cables. Let's take a look at the dangers of electric power cables and what's going on.
　　Power lines and cable fires are dangerous
　　The cause of wire and cable fire is the short circuit, overload, bad contact and external source of fire. After the fire, on the one hand, they cannot guarantee the normal line of power supply, leading to the elevator, emergency lighting, automatic alarm and fire extinguishing system cannot work normally, and give relief evacuation work brings certain difficulties. On the other hand, due to the cable sheath and insulation is composed of various kinds of polymer, the high group at the rear of the fire quickly heating molten, ignition, combustion and decomposition, combustible gas diffusion four stages, caused its shows the following defects in the fire:
　　(1) the amount of gas produced is large
　　Polymer during combustion produces a large amount of smoke and toxic gases, this not only led to reduced visibility, influenced people's evacuation and fire fighting and rescue, and toxic gases directly threatens the fire life safety of the people.
　　(2) to produce corrosive gases, causing "secondary hazards"
　　Polyvinyl chloride (PVC) decomposition of HCL gas not only has toxicity, such as to the scene of the fire at the same time the corrosion effects of electrical and electronic equipment, greatly reduces the equipment security and service life.
　　(3) heat up
　　To determine the cone calorimeter data show that non flame retardant PP always heat about 91.32 MJ/M3, so much of the high temperature radiation hazards to personnel is self-evident.
　　In addition, the cable mainly passes through "silos", "closed channel", because "chimney" or "flash-burning" benefit, the fire spread will be more amazing. And in the cable fire, with polyvinyl chloride (PVC) thermal decomposition, release a large amount of HCL, CL2, HCLO, CO, CO2, etc., will be on the surrounding area and deadly creatures in the range of the fire.
　　The occurrence of electric wires and cable fires
　　In terms of material and type of cable, cable or whether the past the paper now all plastic cable, from the insulation of the cable, cross-linked polyethylene, ethylene propylene rubber and other materials to the oil, hemp, PVC outer sheath material is flammable substances. Especially the polymer material under a certain temperature melting happens, when local cable reach high temperature burning, and more than adjacent cables ignition temperature, can lead to secondary cable group. The cable fire factor is more, there are the following points:
　　(1) there is a lag in the knowledge of cable fire prevention. Because of the regulation of cable construction in our country late, the cable fire standards were not high in the 1980s, some even had no fire prevention measures at all. At present, the design institute is low in cable fire prevention standard, some even have no fire prevention measure at all. At present, the design institute in the cable fire prevention aspect just started, the design content is not comprehensive and perfect. The cable fire prevention problem has not caused the construction installation personnel and the running management personnel should pay attention. Some units for a long time for cable tunnel and cable interlayer and high and low voltage electrical cabinets cable through the hole doesn't make any block, some units only simple materials such as asphalt sealing treatment, such already can not meet the fire requirements and do not conform to the specifications.
　　(2) improper installation of cables. When cable laying, due to construction personnel do not understand or didn't construction in strict accordance with the procedures and process requirements, often caused by scraping, touch, pressure, twist cable outer sheath damage, easy water be affected with damp be affected with damp. At run time, the insulation layer may be punctured to produce an arc, causing a fire to burn.
　　(3) the joint process is not good. Due to some low quality of the cable technician, craft level is poorer, especially for cable accessories varieties, new technology, new material, new process understand the ominous, conductor connection mechanism is unknown, process operation, do not pay attention to health, for magazines, dirt and other clean enough, easy to cause contact interface is bad; For joint production quality is not high, fire prevention measures is less, so that under fault condition, by the impact of high voltage, high current, often leads to joint burst into flames.
　　(4) poor grounding of cable. Caused by a lack of understanding of the importance of cable grounding, docking insufficient recognition of quality, ground wire welding not firm, grounding, resistance is big, thus causing cable grounding fault current is smaller than normal short-circuit current, the current protection device is not to cut off the fault in time, arc, spark occurs. According to the relevant data, 0.15 A current arc, the local heat of the electric spark can cause combustible material to fire.
　　(5) improper management. The failure of the cable inspection system or the failure to enforce the cable inspection system makes many fire hazards untimely to be discovered and excluded. The poor selection of cables, resulting in a prolonged period of overloading or overloading of some cables, makes the temperature rise too high; The operator misoperates or illegally causes short circuit or overloads to multiply the cable's heat, causing the insulation to age or break through the fire.
　　(6) the cables are too crowded. In the design of new and technological upgrading projects, consider lowering costs, less take fire prevention measures, cause the cable laying too concentrated, mixed, serious area, heat dissipation, especially after the light-off will produce toxic smoke in the low voltage cable, together with the high voltage cable tend to cause a little fault continuous burning collapse of serious consequences.
　　Although in the study of flame retardant technology in China in recent years has made great progress, but in the field of wire and cable fire retardant, there is still a gap compared with abroad, needs further research and discussion. With the development of national economy and science and technology, there will be more better fireproofing materials and advanced technology for fire prevention, for cable fire prevention and fire fighting work provide a powerful guarantee.