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How to prevent wire and cable from being overloaded with fire
- May 18, 2017 -

Wire and cable in the process of running, because of the existence of resistance to heat. The resistance of the conductor is generally small, and its calorific power can be expressed by formula Q=I^2R. Q=I^2R shows: For a piece of actual use of the conductor (R has been basically constant), the greater the current through the conductor, the greater the power of the heating; If the electric flow is constant, the heating power of the conductor is constant. The heat emitted during the operation can be absorbed by the conductor itself and cause the wire temperature to rise. While the conductor is running in the process of absorbing current work, the temperature will not be increased without restriction. Because the conductor is endothermic at the same time, also constantly to the outside world, the facts show that the wire after the temperature rises gradually, the last temperature constant at some point. At this constant point, the conductor suction, the radiating power is consistent, the conductor is in the thermal equilibrium state. The ability of conductors to withstand higher temperatures is limited, and there is a danger of exceeding a maximum temperature operation. This maximum temperature naturally corresponds to a maximum current, which is overloaded with the conductor exceeding the maximum current operation. The conductor overload directly causes the conductor itself and the temperature of the goods nearby. Elevated temperatures are the most direct cause of the fires.

The overload causes the insulation of the double-stranded conductor to short-circuit, burn the equipment and trigger the fire. The two-strand conductor is separated by the insulation layer, which softens the insulating layer and causes the failure of the two strands of direct contact to cause a short-circuit, burn damage equipment. At the same time, the high temperature caused by the high current in the short circuit is triggered by fire and fuse, resulting in a fire caused by the melting bead falling into the combustible material. The overload temperature rise can also directly ignite nearby combustible material. The heat transfer of the overload conductor causes the combustible temperature to rise nearby, and it is possible to ignite the fire caused by a lower combustible material nearby. This danger is particularly prominent in the storage of flammable goods and the use of easy and combustible buildings.

Overload also causes the connections in the circuit to be overheated, which speeds up the oxidation process. Oxidation makes the connection point to produce a thin a-layer oxidation film, the oxide film increases the resistance between the contact point, resulting in a fire and other phenomena, causing fires.
So, how to prevent a wire and cable overload and fire?

1, in the line design process, should accurately approve the site capacity, fully consider the possibility of new capacity, select the appropriate model of the wire. Large capacity, should choose thicker conductor. Line design, reasonable selection is the key step to prevent overload. If the design of improper selection, will be left to rectify the congenital hidden dangers. Some small projects and places do not carefully design selection. It is very dangerous to choose and lay the wires freely. New electrical appliances and equipment should fully consider the bearing capacity of the original line. The original line does not meet the requirements, should be redesigned and reformed.

2, the line should be in accordance with the relevant specifications, so that electrician qualified personnel construction laying. The laying condition of the line directly affects the heat dissipation of the conductor. Generally speaking, the wiring should not traverse easy, combustible substances, stacking, which will lead to the conductor heat dissipation, heat accumulation, the possibility of producing combustible goods around the ignition is increased, the danger of fire is caused by overload. The laying line of the decoration ceiling of public entertainment venues should be protected by steel pipe, so that the ceiling and the line separated, in overload, short-circuit and so on, even if the bead will not fall, to avoid the fire.

3, strengthen the power management, avoid disorderly wiring, disorderly lap line, cautious use of mobile socket. Disorderly wiring, disorderly lap line, use of mobile socket is actually a certain line on the addition of electrical equipment, increase the electricity flow and can cause overload. Mobile socket jack is more than the wall of the fixed socket, if the use of excessive electrical equipment on the mobile socket, the original line must be unbearable. For more high-power equipment, electrical appliances should be set up separate lines, not use mobile socket as the wiring source.

4, speeding up the renewal of old line, eliminating the fire hazard. Old enterprises, old residential areas and other units, because of the use of more distant time, many lines have been aging, exceeding the age of use. The load flow of some circuits is not even small, but the aging line is difficult to withstand such load flow, also has the danger of overloading. In particular, old residential areas, the line has long been aging, but with the improvement of people's living standards, the increase in household appliances, the amount of electricity is still rising year, is worse. For the old lines, should be promptly urged and coordinated, as soon as possible to promote its rectification, to eliminate fire hazards, to ensure security.