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Under what circumstances can a fire occur due to overheating (dangerous temperature)?

Overloading can cause electrical equipment to overheat. Due to unreasonable design and selection of circuits or social equipment, or failure to consider appropriate margins, it may overheat under normal load. Due to unreasonable use, that is, the load of the line or equipment exceeds the rated value, or the continuous use time is too long, and the design capacity of the line or equipment is exceeded, causing overheating; lax management and random connection may easily cause overload operation of the line or equipment. When the breaking capacity of the oil circuit breaker cannot meet the requirements, it will cause a fire or explosion. Fault operation of equipment will cause equipment and circuit overload. For example, three-phase motor running without one phase or asymmetrical operation of three-phase transformer may cause overload.

The contact part is the weak link in the circuit and a key part of overheating. fire hose adapter and fitting  Unremovable joints are not firmly connected, poorly welded, or mixed with impurities at the joints, which will increase the contact resistance and cause the joints to overheat. Removable joints that are not tightly connected or loose due to vibration can also cause the joints to heat up. Movable contacts, such as knife switch contacts, contactor contacts, plug-in fuse contacts, plug contacts, bulb and lamp holder contacts, etc., if there is not enough contact pressure or contact Rough and uneven surfaces can cause the joint to overheat. The sliding contact of the brush should be kept under sufficient pressure, and should be kept smooth and clean to prevent excessive sparks.

The iron core of transformers, motors and other equipment, such as iron core insulation damage or long-term overvoltage, its eddy current loss and hysteresis loss will increase and overheat.   All kinds of electrical equipment are designed and installed with certain heat dissipation or ventilation measures. If these measures are damaged, it will cause the equipment to overheat. If the oil pipe is blocked, the ventilation duct is blocked or the installation position is not good, it will cause poor heat dissipation and cause overheating.  The leakage current is generally not large, and the line fuse will not operate. If the leakage current is roughly evenly distributed along the line, the heat will be dispersed and the fire risk is not great; if the leakage current is concentrated at a certain point, it will easily cause a fire. Leakage current is often caused by metal screws or nails to cause wooden components to catch fire.

Electric heating appliances are electrical equipment that converts electrical energy into heat. The working temperature of the resistance wire of the electric furnace is as high as 800℃, which can ignite combustible materials in contact with or nearby. The baking time of the items in the electric oven is too long, and the temperature is too high, which may cause a fire. When using infrared heating device, if the infrared beam is irradiated on combustible material by mistake, it will cause burning. The high working temperature of lamps and bulbs, such as improper installation and use, may cause fire and explosion accidents.

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