Initial Cause of Distribution Box Fire
First, the causes of distribution box fire mainly include the following four aspects:
1. Leakage fire: The so-called leakage of electricity means that the insulation ability of the wire or the bracket material decreases due to some reasons (natural or man-made reasons, such as wind and rain, humidity, high temperature, bumping, scratching, friction, corrosion, etc.), resulting in the loss of insulation between the wire and the wire (through damaged insulation, branches, etc.). There is a part of the current between the conductor and the earth (the wire passes through the steel bar of the cement wall, the tinplate of the horse mouth, etc.). This phenomenon is the leakage of electricity. When the leakage occurs, the leakage current will produce local high temperature in the way of flowing into the earth, if it meets the parts with larger resistance, which will cause the nearby combustibles to ignite, thus causing fire. In addition, the leakage sparks generated at the leakage point can also cause fire.
2. Short-circuit fire: When the insulator of bare conductor or insulating conductor is damaged in electric line, the fire line collides with the adjacent line, or the fire line and ground line (including grounding subordinate to the earth) at a certain point, which causes a sudden large increase in current, it is called short-circuit, commonly known as collision line, mixed line or connecting electricity. Because of the sudden decrease of resistance and the sudden increase of current when short circuit occurs, the instantaneous calorific value is also very large, which greatly exceeds the calorific value of the normal operation of the line. It is easy to generate strong sparks and arcs at the short circuit point. It can not only make the insulating layer burn rapidly, but also make the metal melt, and cause the flammable combustibles nearby to burn. A fire broke out.
3. Overload fire: The so-called overload refers to the phenomenon that the temperature of the conductor increases continuously when the current in the conductor exceeds the safe carrying capacity. This phenomenon is called conductor overload. When the conductor is overloaded, the aging and deterioration of the insulating layer of the conductor are accelerated. When the conductor is seriously overloaded, the temperature of the conductor will continue to rise, even cause the insulation of the conductor to burn, and can ignite the combustibles near the conductor, thus causing fire.
4. Fire of excessive contact resistance: It is well known that there are joints where wires and wires, wires and switches, fuses, instruments, electrical equipment and so on are connected. The resistance formed on the contact surface of joints is called contact resistance. It's normal to heat up when current passes through the joint. If the joint is well treated and the contact resistance is not large, the heat at the joint point is very small and the normal temperature can be maintained. If there are impurities in the joint, the connection is not reliable or other reasons make the joint contact bad, resulting in the contact part of the local resistance is too large, when the current passes through the joint, there will be a lot of heat, forming high temperature, this phenomenon is the contact resistance is too large. If the contact resistance is too large in a certain place, it will generate great heat in the local area where the contact resistance is too large, which will discolor or even melt the metal, cause the insulation layer of the conductor to burn, and lead to the combustion of combustibles or dust deposited on the conductor nearby. Fiber and so on, thus causing fire.
Second, Prediction of Distribution Box Fire
Before the distribution box is on fire, there is a kind of precursor, which should be paid special attention to. Because of overheating, the insulating skin of the wire will be burned first, and a bad smell of burning rubber and plastic will be emitted. Therefore, when smelling this odor, we should first think that it may be caused by electrical reasons. If we can't find other reasons, we should immediately pull the switch and cut off the power supply, until we find out the reasons and properly handle them, then we can switch on and send the power.
If we can understand the cause of distribution box fire well, we can avoid the fire from the source. If we pay more attention to the situation of distribution box before the fire happens, it can also kill the fire in the budding state.
