Question 1: What are the main causes of electrical fires? Electrical fires mainly come from three aspects.
1. Short circuit. During a short circuit, the current quickly rises to 10-15 times the rated current, causing the wire circuit to be severely overloaded and overheated, leading to a fire.
2. Overload. Electrical overload, the electrical itself and the circuits heat and burn due to overload, leading to fires.
3. Static electricity and arc. When stacking flammable items or gases, arcs generated due to static electricity or poor contact may ignite the flammable items or gases and cause fires.
Question 2: What are the main causes of electrical fires?
(1) Inflammable and explosive environments
In daily life and industry In production, flammable and explosive substances widely exist, especially in petroleum, chemical industry, coal mines and military industry production. In some production sites, there are flammable gases, dust or fibers, which will ignite when exposed to a fire source, and will ignite during production. , it is easy to mix with air during storage, transportation and use to form explosive mixtures. There are hundreds of substances that can form explosions. There are more types of substances that can cause fires. Once managed and used improperly, electrical fires will occur when electrical faults occur.
(2) Reasons for high temperatures in electrical equipment
Sparks and high temperatures generated by electrical equipment can easily cause fires. The reasons for high temperatures in electrical equipment are as follows:
1 Some When electrical equipment is working normally, it can produce sparks, arcs and high temperatures. For example, the pulling and closing operations of electrical switches, electric furnaces, incandescent lamps, welding machines, etc. all work at very high temperatures and produce arcs.
2. Short circuit occurs in lines and electrical equipment, resulting in high temperature and arc.
3 Overloading of electrical circuits can cause fires. The electrical circuit is overloaded, for example: the fuses and circuit breakers are too large and do not operate. Over time, the insulation will be destroyed due to overheating, causing fire.
4 Due to oxidation corrosion of electrical equipment contacts and electrical circuit joints, short connection length, quality of electrical equipment and other reasons, the contact pressure is too small, resulting in poor contact, sparks, arcs and dangerous high temperatures during operation, causing fires .
5. Static discharge sparks can also cause fires.
6 Fires are caused by faults in electrical equipment during operation, such as inter-turn short circuits, inter-layer short circuits, inter-phase short circuits in transformers, motors, coils and other equipment. Dangerous high temperatures burn the insulation and cause fires.
Question 3: What are the main causes of electrical fires?
(1) Inflammable and explosive environments
In daily life and In industrial production, flammable and explosive substances widely exist, especially in petroleum, chemical industry, coal mines and military industry production. In some production sites, there are flammable gases, dust or fibers, which will ignite when exposed to a fire source, and will ignite when exposed to a fire source. During production, storage, transportation and use, it is easy to mix with air to form explosive mixtures. There are hundreds of substances that can form explosions. There are more types of substances that can cause fires. Once managed and used improperly, electrical fires will occur when electrical faults occur.
(2) Reasons for high temperatures in electrical equipment
Sparks and high temperatures generated by electrical equipment can easily cause fires. The reasons for high temperatures in electrical equipment are as follows:
1 Some When electrical equipment is working normally, it can produce sparks, arcs and high temperatures. For example, the pulling and closing operations of electrical switches, electric furnaces, incandescent lamps, welding machines, etc. all work at very high temperatures and produce arcs.
2. Short circuit occurs in lines and electrical equipment, resulting in high temperature and arc.
3 Overloading of electrical circuits can cause fires. The electrical circuit is overloaded, for example, the fuses and circuit breakers are too large and do not operate. Over time, the insulation will be destroyed due to overheating, causing fire.
4 Due to oxidation corrosion of electrical equipment contacts and electrical circuit joints, short connection length, quality of electrical equipment and other reasons, the contact pressure is too small, resulting in poor contact, sparks, arcs and dangerous high temperatures during operation, causing fires .
5. Static discharge sparks can also cause fires.
6 Fires are caused by faults in electrical equipment during operation, such as: inter-turn short circuits, inter-layer short circuits, inter-phase short circuits in transformers, motors, coils and other equipment, which can cause dangerous high temperatures and burn the insulation and cause fires.
Question 4: What are the causes of electrical fires? Answer: The main causes of electrical fires include short circuit, overload, excessive contact resistance, leakage, improper use of electric heaters, static electricity and lightning.
Question 5: What are the main causes of electrical fires 1. Overheating Overheating of electrical equipment is primarily caused by the heat generated by electrical current.
Although the resistance of a conductor is very small, its resistance always exists objectively. Therefore, when electric current passes through a conductor, it consumes a certain amount of electrical energy. This part of the electrical energy is converted into heat energy, which increases the temperature of the conductor and heats other materials around it. For electrical equipment with ferromagnetic materials such as motors and transformers, in addition to the heat generated by the current passing through the conductor, there is also heat generated in the ferromagnetic material. Therefore, the iron core of this type of electrical equipment is also a heat source.
When the insulation performance of electrical equipment is reduced, the leakage current through the insulating material increases, which may cause the temperature of the insulating material to rise.
From the above analysis, it can be seen that electrical equipment always generates heat when running. However, for electrical equipment that is designed, constructed correctly and operates normally, its maximum temperature and the temperature difference between it and the surrounding environment (that is, the maximum temperature rise) ) will not exceed a certain allowable range. For example: the maximum temperature of bare conductors and plastic insulated wires generally does not exceed 70°C. In other words, normal heating of electrical equipment is allowed. However, when the normal operation of electrical equipment is damaged, the amount of heat generated will increase and the temperature will rise. When certain conditions are reached, a fire may occur.
Abnormal operation that causes overheating of electrical equipment generally includes the following situations: (1) Short circuit. When a short circuit occurs, the current in the line increases to several times or even dozens of times the normal level, causing the temperature of the equipment to rise sharply, greatly exceeding the allowable range. If the temperature reaches the self-ignition point of combustible materials, combustion will occur, leading to fire. The following are some common situations that cause short circuits: the insulation of electrical equipment ages and deteriorates, or loses its insulation ability due to high temperature, moisture, or corrosion; when insulated wires are directly wound or hooked on iron nails or wires, the insulation becomes damaged due to wear and iron corrosion. , causing insulation damage; improper installation of equipment or negligent work, causing mechanical damage to the insulation of electrical equipment; the insulation of electrical equipment may be broken down due to overvoltage such as lightning strikes; during installation and maintenance work, due to improper wiring and operation Error etc. (2) Overload. Overload will cause the electrical equipment to heat up, and there are generally two reasons for overload: First, the lines or equipment are unreasonably selected during design, resulting in overheating under the rated load; second, the use is unreasonable, that is, the load of the lines or equipment Exceeding the rated value, or using it continuously for too long, exceeds the design capacity of the circuit or equipment, resulting in overheating. (3) Poor contact. The contact part is a key part where overheating occurs and can easily cause local heating and burning. The following situations can easily cause poor contact: non-detachable joints are not firmly connected, are poorly welded, or have impurities mixed in the joints, which will increase the contact resistance and cause the joints to overheat; detachable joints are not tightly connected or become loose due to vibration. Will cause the joint to heat up; movable contacts, such as the contacts of the knife switch, the contacts of the plug, the contact between the bulb and the lamp holder, etc., if there is not enough contact pressure or the contact surface is rough and uneven, it will cause the contact Overheating; for copper-aluminum joints, due to the different electrical properties of copper and aluminum, the joints are prone to corrosion due to electrolysis, resulting in overheating of the joints. (4) The iron core heats up. If the core insulation of transformers, motors and other equipment is damaged or subjected to long-term overvoltage, eddy current loss and hysteresis loss will increase, causing the equipment to overheat. (5) Poor heat dissipation. Certain heat dissipation or ventilation measures must be taken into consideration when designing and installing various electrical equipment. If these parts are damaged, it will cause the equipment to overheat. In addition, electrical equipment such as electric furnaces that directly use the heat of electric current to work has relatively high operating temperatures. If installed or used improperly, it may cause a fire.
2. Electric sparks and arcs. Generally, the temperature of electric sparks is very high, especially electric arcs. The temperature can be as high as 3000℃ to 6000℃. Therefore, electric sparks and arcs can not only cause the burning of combustibles, but also melt and splash metal, posing a dangerous hazard. source of fire. In places with explosion risks, sparks and arcs are a very dangerous factor causing fires and explosions.
Electric sparks generally include working sparks and accident sparks. Working sparks refer to electrical equipment generated during normal operation or during normal operation. Such as sparks generated when the switch or contactor is opened and closed, sparks generated when the plug is pulled out or inserted, etc. Accident sparks occur when wiring or equipment fails. Such as sparks that occur when a short circuit or grounding occurs, flashes that occur when insulation is damaged, sparks that occur when wire connections are loose, sparks that occur when fuses blow, overvoltage discharge sparks, static electricity sparks, and sparks caused by incorrect operations during repair work, etc.
In addition, there are mechanical sparks caused by collisions; when a light bulb breaks, the hot filament has a dangerous effect similar to sparks. ......>>
Question 6: What are the causes of electrical fires? Answer: The main causes of electrical fires are short circuit, overload, excessive contact resistance, leakage, improper use of electric heaters, Static electricity and lightning.
Question 7: What are the causes of electrical fires? The main causes of electrical fires are short circuit, leakage, overload, and electrical aging. Measures need to be taken to prevent the occurrence of electrical fires based on specific circumstances.
Question 8: What are the causes of short circuits that cause electrical fires?
Question 9: What are the main causes of electrical fires? The main cause of electrical fires is wires or electrical appliances caused by large currents. Overheating may ignite electrical appliances or surrounding flammable materials. Therefore, controlling the current in wires to prevent overload and short circuit is the most important method.