■ Analysis and discussion on the leakage of transformer oil
With the development of the power industry, how to improve the performance of power equipment and ensure the reliable operation of the power system is an urgent problem that needs to be solved in power production. Therefore, whether the leakage of transformer oil can be timely and thoroughly dealt with has gradually become an important technical indicator to measure the development of the power industry. The phenomenon of oil leakage in oil-immersed power transformer is quite common in power system. If there is oil leakage in transformer, it may affect the safe and stable operation of transformer. How to solve the problem of leakage oil of transformer is a big problem in the production practice of power sector for many years.
1. Analysis of the causes of transformer oil leakage
According to operation experience, transformer leakage oil generally occurs in the following seven main parts: ① the body large cover connection surface; ② Radiator; ③ Sampling valve; ④ casing; ⑤ tubing flange face; ⑥ transformer base interface; ⑦ Gas relay, etc. It can be found that most of the leakage points are flange joints, seals and valves. Unreasonable flange structure, poor sealing material quality, poor processing technology, changes in the external environment temperature, pressure, etc. will cause leakage of the transformer. These factors complement each other and have a common impact. When there is a problem in one of the links, it will cause a chain reaction, resulting in the occurrence of leaking oil. In practice, the following specific analyses are carried out:
First, the flange surface manufacturing process is unreasonable, and the leakage point at the oil drain plug of the transformer radiator interface accounts for more than half of the total leakage point. The reasons of leakage are: (1) there are corrosion, burr, groove and other phenomena on the contact surface; (2) No sealing groove, unlimited pin; (3) Paint and other dirt on the contact surface; When dealing with paint debris, it may scratch scars on the sealing surface; (4) The position and tightness of the sealing ring are completely determined by experience, and too loose and too tight may lead to leakage.
Second, the most commonly used sealing material is butyl rubber, which is made of sealing rings and gaskets with poor oil resistance and faster aging speed, especially at high temperatures, which can easily cause aging cracking and loss of elasticity. In addition, due to the uneven finish of the sealing surface during the installation process, the compression amount is increased and the leakage is caused.
Third, the transformer shell manufacturing process and material quality, if the transformer shell there are pores, sand holes, welding, welding phenomenon will cause leakage of transformer oil.
Fourth, the connection surface of the plate butterfly valve is rough and thin, and there is only a single layer seal, which causes leakage of the transformer.
The fifth is the influence of temperature. When the external temperature is low, the transformer installed in the summer is not, after the summer (temperature up to 37 ° C) operation, the installation of a very tight seal due to the thermal expansion of the metal increases the compression amount, and when the winter temperature is reduced (the minimum can reach -4 ° C), the elasticity of the seal is reduced, and the compression is reduced, resulting in leakage.
Second, type analysis of transformer leakage oil
1. Air leakage. It's an invisible leak. For example, the leakage of air in and out of the casing head, the diaphragm of the oil storage tank, the glass of the safety airway, and the sand hole of the weld. The moisture and oxygen in the air slowly penetrate into the body through the leaking part, and the sealing inside and outside of the transformer is damaged, causing problems such as moisture insulation and accelerated aging of oil.
2. Oil leakage. One is internal leakage. Oil in the bushing or oil in the on-load tap changer chamber leaks into the transformer body. The second is external leakage. Weld leakage and seal leakage, this is the most likely and the most common leakage phenomenon.