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      How to prevent wire and cable from catching fire due to wire overload?Date: 2019-10-19  Source: Dewei

      During the operation of the wire and cable, heat is generated due to the presence of electrical resistance. The resistance of the wire is generally small, and its heating power can be expressed by the formula q=I^2R. q=I^2R indicates that for a wire in actual use (R is almost constant), the larger the current through the wire, the greater the heating power; if the current is constant, the heating power of the wire is also constant. . The heat released during operation is absorbed by the wire itself causing an increase in the temperature of the wire. Although the wire is continuously absorbing the heat released by the work during operation, its temperature does not rise without limit. Because the wire is constantly radiating heat to the outside while it is absorbing heat, it turns out that the temperature gradually rises after the wire is energized, and finally the temperature is constant at a certain point. At this constant point, the wire draw and discharge heat are consistent, and the wire is in thermal equilibrium. The ability of a wire to withstand higher temperatures is limited, and operation above a certain maximum temperature can be dangerous. This maximum temperature naturally corresponds to a certain maximum current, and the wire is overloaded when it exceeds this maximum current. Wire overload directly causes the temperature of the wire itself and its nearby items to rise. The increase in temperature is the most direct cause of this type of fire.

      The overload causes the insulation between the double-stranded wires to cause a short circuit, which burns the equipment and causes a fire. The double-stranded wires are separated by an insulating layer therebetween, and the overload causes the insulating layer to soften and break, thereby causing direct contact between the two wires to cause a short circuit and burning the device. At the same time, the high temperature generated by the large current at the moment of short circuit causes the line to ignite and melt, and the generated beads fall to the combustibles to cause a fire. The overload temperature rise can also directly ignite nearby combustibles. The heat transfer of the overloaded conductor raises the temperature of the nearby combustibles, and it is possible to ignite the flammable materials with low ignition points nearby. This hazard is particularly acute in warehouses where flammable materials are stored and in buildings that are easy to use and flammable.

      Overloading also places the connections in the line under overheating conditions, which accelerates the oxidation process. Oxidation causes a thin oxide film that is not easily conductive at the joint, and the oxide film increases the electric resistance between the contact points, thereby causing a phenomenon such as sparking and causing a fire.

      So how do you prevent fires caused by overloading wires and cables?

      1. In the circuit design process, the capacity of the site should be accurately verified, and the possibility of adding capacity in the future should be fully considered, and the appropriate type of wire should be selected. Large capacity, should choose a thicker wire. Circuit design and reasonable selection are the key steps to prevent overload. If the design is not properly selected, it will leave a congenital hidden danger that is difficult to rectify. Some small projects and places are not carefully designed and selected. It is very dangerous to choose and lay the line at will. New electrical appliances and electrical equipment should fully consider the bearing capacity of the original line. If the original line does not meet the requirements, it should be redesigned and modified.

      2. The line should be laid in accordance with the relevant specifications and allowed to be laid by an electrician qualified personnel. The laying conditions of the line directly affect the heat dissipation of the wire. Generally speaking, the laying of the line should not pass through the easy, combustible materials, stacking, which will lead to poor heat dissipation of the wires, heat accumulation, the possibility of igniting the surrounding combustible articles, and increase the risk of fire caused by overload; The lines laid in the ceiling of public entertainment venues shall be protected by steel pipes so that the ceilings are separated from the lines. In the event of overload or short circuit, even if there are beads, they will not fall and avoid fire.

      3. Strengthen power management, avoid messy wiring, messy lines, and use mobile sockets with caution. Indiscriminate wiring, chaotic wiring, and the use of mobile sockets are actually adding electrical equipment to a certain line, increasing the amount of current and possibly causing overload. The mobile socket jack is obviously more than the fixed socket on the wall. If too many electrical equipment is used on the mobile socket, the original line must be unbearable. For larger power equipment and electrical appliances, separate lines should be provided, and mobile sockets should not be used as wiring sources.

      4. Accelerate the renovation of old lines and eliminate fire hazards. Old enterprises, old residential areas and other units, due to the long time of use, many lines have been aging, exceeding the service life. Even if the current carrying capacity of some lines is not large, the aging line is difficult to withstand such current carrying capacity, and it also has the danger of overload. Especially in the old residential areas, the lines have long since aging, but with the improvement of people's living standards and the increase of household appliances, their electricity consumption is still rising year by year, which is really worse. For old lines, we should promptly supervise and coordinate, and promote their rectification as soon as possible to eliminate fire hazards and ensure safety

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      Dongguan Dewei Wire Co., Ltd
      Contact: Mr. Li +86-13922913367
      Tel: +86-769-85472388
      Fax: +86-769-85472688
      E-mail: dewei@dgtechway.com
      Add: No. 116, Jinghai West Road, Shatou South District, Chang'an Town, Dongguan City, Guangdong Province

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