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How to prevent wire and cable from catching fire due to wire overload

by:AAA     2020-03-02
During the operation of wires and cables, they will heat up due to the presence of resistance. The resistance of the wire is generally very small, and its heating power can be expressed by formula q = I 2R. Q = I 2R indicates that for a section of wires in actual use (R has been basically constant) , The greater the current through the wire, the greater the heating power; If the current flow is constant, the heating power of the wire is also constant. The heat released during operation will be absorbed by the wire itself, thus causing the temperature of the wire to rise. Although the conductor is constantly absorbing the heat released by the current during operation, its temperature will not rise indefinitely. Because while the wire is absorbing heat, it is also constantly releasing heat to the outside world. The facts show that the temperature of the wire gradually rises after the power is turned on, and the final temperature is constant at a certain point. At this constant point, the heat absorption and heat release power of the wire are consistent, and the wire is in a state of heat balance. There is a limit to the ability of wires to withstand higher temperatures, and there will be danger if they exceed a certain maximum temperature. This maximum temperature naturally corresponds to a certain maximum current, and the operation of the wire exceeding this maximum current is overload. The overload of the wire directly causes the temperature rise of the wire itself and its nearby articles. Temperature rise is the most direct cause of this kind of fire. Overload causes short circuit caused by the damage of insulation layer between double-stranded wires, burning equipment and causing fire. The double-strand conductor is separated by the insulation layer between them, and the overload softens and destroys the insulation layer, thus causing the direct contact of the two wires to cause short circuit and burn the equipment. At the same time, the high temperature generated by large current at the moment of short circuit makes the line fire and fusing, and the generated molten bead falls to combustible to cause fire. Overload temperature rise can also directly ignite nearby combustibles. The heat transfer of the overload conductor raises the temperature of the nearby combustibles. For the combustibles with lower ignition point nearby, it is possible to ignite them and cause fire. In the storage of flammable materials in the warehouse and easy to use, combustible decoration of the building, this kind of risk is particularly prominent. Overload also makes the connection in the line under the condition of overheating, which accelerates the oxidation process. Oxidation makes a thin oxide film which is not easy to conduct electricity at the connection point, and the oxide film increases the resistance between the contact points, thus causing ignition and other phenomena, causing fire. So, how to prevent fire caused by wire and cable overload? 1. In the process of line design, the capacity of the site should be accurately verified, the possibility of adding capacity in the future should be fully considered, and the appropriate type of conductor should be selected. Large capacity, should choose a thicker wire. Line 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 lines at will. New electrical appliances and electrical equipment should fully consider the bearing capacity of the original line. The original line does not meet the requirements, should be redesigned, transformation. 2, the line should be in accordance with the relevant specifications, let the electrician qualified personnel construction and laying. The laying conditions of the line directly affect the heat dissipation of the conductor. Generally speaking, the line laying should not pass through easy and combustible substances and stacking, which will lead to poor heat dissipation of wires and accumulation of heat, resulting in the possibility of igniting combustible articles around, the risk of fire caused by overload is increased; The lines laid in the decorated suspended ceilings in public entertainment places should be protected by steel pipes to separate the suspended ceilings from the lines. Even if there are molten beads in overload and short circuit, they will not fall off to avoid fire. 3. Strengthen the management of electricity consumption, avoid random wiring and wiring, and carefully use mobile sockets. Random wiring, random wiring, and the use of mobile sockets are actually the addition of electrical equipment to a certain section of the line, which increases the current flow and may cause overload. The number of mobile Socket Jacks is obviously more than that of fixed sockets on the wall. If too much electrical equipment is used on the mobile socket, the original line must be unbearable. For high-power equipment and electrical appliances, separate lines should be set up, and Mobile sockets should not be used as wiring sources. 4, speed up the renovation of the old line, eliminate fire hazards. Old enterprises, old residential areas and other units, due to the use of time is relatively long, many lines have been aging, more than the service life. Even if the current-carrying capacity of some lines is not large, the aging lines cannot bear such current-carrying capacity and have the risk of overload. Especially in the old residential areas, the lines have long been aging, but with the improvement of people's living standards and the increase of household appliances, their electricity consumption is still increasing year by year, which is really worse. For the old line, should be timely supervision, coordination, as soon as possible to promote its rectification, in order to eliminate fire hazards, to ensure safety.
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