Problems needing attention in the work of high frequency and low frequency transformers

　　 (1) Leakage treatment. The leakage of high-frequency and low-frequency transformers is divided into oil-side leakage and gas-side leakage. Generally speaking, oil leakage is the leakage of oil in the tank (or casing) into the atmosphere, which belongs to oil-side leakage; Leakage into the tank or casing is air side leakage. Any part filled with oil may leak on the oil side. Leakage on the oil side is characterized by traces of residual oil at the leak, which contaminates the appearance of the transformer. When the oil pressure at the leak is greater than the osmotic pressure of the oil solution (contaminated oil), moisture, gas and other impurities in the atmosphere cannot invade the inside of the tank; when the oil pressure at the leak is less than the osmotic pressure of the oil solution, Intermolecular interpenetration occurs, and atmospheric moisture, gas and other impurities may penetrate into the fuel tank. Gas side leakage occurs in the parts where there is gas in the transformer, such as the upper end of the high-voltage bushing copper pipe, the part above the oil level of the safety air passage, the air cavity left on the top of the transformer with oil, and the upper part of the oil chamber of the oil conservator , The negative pressure area of the strong oil circulation, the upper part of the casing oil conservator. The characteristic of air-side leakage is due to the thermal expansion and contraction of the stored gas, and the "breathing" is performed at the leakage. When sucking into the atmosphere, the moisture, gas and other impurities in the atmosphere are sucked into the inside of the oil tank or casing.

Especially in rainy and snowy weather, a lot of moisture may be sucked in at one time, causing partial moisture of the insulation, lowering the dielectric strength of the insulation, and causing breakdown discharge. Since gas leakage does not leave traces like oil leakage and cannot be detected by the naked eye, the probability of an accident is very high, and the consequences are particularly serious. The oil-paper insulation of the transformer or bushing is the insulation that is sealed from the atmosphere. Because "its electrical strength has nothing to do with atmospheric conditions", it belongs to "internal insulation". When leakage occurs on the gas side or the oil side, the electrical strength is related to atmospheric conditions. Therefore, the leakage of the transformer or bushing is a kind of damage to the internal insulation. The decrease or even loss of the insulation strength caused by leakage is a more serious damage to the internal insulation.

(2) Maintenance of the plastic bag sealing oil pillow. In order to slow down the oxidation of transformer oil, a diaphragm or capsule (also known as a plastic bag) is placed on the oil surface of the oil pillow. The upper mouth of the capsule is in communication with the atmosphere, so that the oil surface of the oil pillow is completely isolated from the atmosphere. The change in oil temperature increases or decreases. When refueling the oil pillow, pay attention to exhaust the air between the outside of the capsule and the inner wall of the oil pillow as much as possible, otherwise, it will cause false oil level and the action of the Buchholz relay, so the oil should be fully sealed. When refueling the oil pillow, pay attention to the proper amount of oil and the oil inlet speed to prevent the oil speed from being too fast. When the oil amount is too high, it may cause the explosion-proof pipe to inject oil, the pressure releaser to signal or inject oil.

(3) Operation and maintenance of the oil purifier. There is a flange joint on the upper and lower part of the transformer box, and a metal bucket filled with silica gel or activated alumina is installed between the two flange joints. The maintenance work mainly includes: When the transformer is running, check the upper and lower valves of the oil purifier in the open position to keep the oil flowing smoothly. The silica gel in the oil purifier should be replaced after a long period of use and replaced with qualified silica gel. When the oil purifier is put into operation, first open the lower valve to fill the oil purifier with oil, and open the small exhaust valve on the upper part of the oil purifier to let the air out. When the small valve overflows, the small valve can be closed. Open the valve on the oil purifier.

　　 Conclusion

The normal operation of high-frequency and low-frequency transformers not only depends on the structural design and manufacturing process of the transformer, but also has a lot to do with daily operation, maintenance and management. Transformer failures are extremely harmful to the operation of the grid system. In order to avoid accidents, The daily operation inspection management should be strengthened and effective maintenance measures should be formulated to ensure the safe and stable operation of the transformer.