The hottest transformer fire accident and Counterm

Transformer fire accidents and Countermeasures

oil immersed transformers are widely used in factory distribution systems because of their low energy consumption and high operation efficiency. They are extremely important electrical equipment in transmission and distribution systems. At present, our company has more than 800 transformers, most of which are oil immersed transformers, which play an important role in the production of power transmission and distribution systems. However, due to the particularity of the internal insulating material of the oil immersed transformer and a large amount of combustible insulating oil, once a serious overload, short circuit and other faults occur in the transformer, it will not only burn the transformer, but also the internal pressure of the transformer will increase sharply due to the rapid vaporization of the insulation and oil under the action of the arc, which may cause damage to the transformer, or fire and explosion, and a large amount of oil injection can further expand the fire. Our factory adopts continuous production mode, with full production load, and the production site is mostly in Grade 1 and 2 fire and explosion-proof areas, so it is increasingly important to prevent transformer fire accidents. In recent years, transformer fire accidents have also occurred in our factory, which has a great impact on production and life. This paper discusses and analyzes the causes of transformer fire and how to prevent it, hoping to help prevent transformer fire accidents

various forms of transformer fire accidents and their countermeasures (2)

1 short circuit fault

transformer short circuit fault may have the following forms: ① transformer internal winding short circuit. The internal winding short circuit of transformer includes polyphase short circuit of winding, single-phase inter turn short circuit, single-phase grounding short circuit, etc. When the internal winding of the transformer is short circuited, the insulation and oil will vaporize rapidly under the action of the arc, which will increase the internal pressure of the transformer sharply, and it is easy to cause the explosion of the transformer oil tank. Not only 2. Check whether the steel bar bending tester and the pedestal are solid and fixed, which will burn the transformer, but also cause a fire accident and further expand the accident. ② When there is a phase to phase short circuit or a phase to phase shell short circuit in the external insulating bushing and outgoing line of the transformer, it will produce a large short-circuit current, accelerate the aging of the coil insulation, and even cause internal faults, resulting in accidents. ③ When the transformer has a short circuit of external load, the transformer will bear a short-circuit current dozens of times the normal current, which may cause mechanical stress in the winding, and the mechanical stress is proportional to the square of the current. The short-circuit current dozens of times will produce a mechanical stress hundreds of times higher than the normal stress. Such a large mechanical stress will deform the winding and cause transformer failure. If the transformer cannot be cut off in time, it will cause an explosion, Fire accident occurs. For example, for a transformer with an impedance of 5%, when the short circuit occurs under the maximum voltage, the initial short-circuit stress is 400 times that of the normal full load state of the main components used on machinery and vehicles. Such a high mechanical stress makes the winding easily deformed, resulting in 3 Plastic: it is suitable for measuring the sliding friction and wear properties of plastics and plastic and other composite materials. If there is a fault in the transformer, it may cause a fire

2. The axial test force of the testing machine should be checked by the local measurement department (or the measurement inspection station of our factory) every 1-2 years.

corresponding countermeasures: ① the insulation strength test should be carried out for the transformer before operation. After the test is qualified, it can be put into use, and gas relay protection should be added inside the transformer. ② The insulation test shall be carried out before the transformer is put into operation, and it can be put into use only after it is qualified. ③ Short circuit protection must be installed between the transformer and the load. For line transformers, drop fuses are generally set at the high-voltage side, and for distribution station systems, high-voltage fuses are set at the outlet side of the high-voltage switchgear. However, the selection of fuse melt must ensure that the fuse can fuse and play a protective role in case of a short circuit in the outgoing circuit of the transformer

2 overvoltage

overvoltage may have two forms: Internal Overvoltage and external overvoltage: ① transformers are generally connected with overhead lines, which may be impacted by external overvoltage caused by natural lightning strike in thunderstorm weather. For 10kV distribution system, the overvoltage amplitude can reach 300~400kv, and this impulse voltage is enough to burn the transformer directly. ② When the transformer is connected with the high-voltage distribution cabinet, some parameters of the power system may change when it is fully switched, switched off and grounded by arc light. In the transition process of parameter changes, power frequency resonance will be generated to cause electromagnetic oscillation, which will produce Internal Overvoltage and impact the transformer. This impact basically presents the form of transmission wave with high amplitude and steep front, and often a series of shock waves pass through each other quickly. Due to the high amplitude of the shock wave, the overvoltage amplitude of the 10kV distribution system can reach several hundred kilovolts. When they reach the transformer winding, the transformer will be seriously impacted, which may cause the internal insulation breakdown of the transformer, cause serious damage to the transformer, and even burn the transformer and cause a fire

corresponding countermeasures: ① when the transformer is connected with the overhead line, the lightning conductor shall be erected on the same pole during the installation of the overhead line. The connection point of the transformer and the overhead line shall be installed with valve type lightning arrester according to the requirements of the national design code, and it shall be tested before the thunderstorm season, and it shall be put into use after it is qualified. ② When the transformer is connected with the high-voltage distribution cabinet, a valve type lightning arrester shall be installed on the high-voltage distribution cabinet, which shall match the insulation of the whole distribution station