Treatment and maintenance of transformer oil

2022-07-26
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Discussion on treatment and maintenance of transformer oil at present, a relatively advanced membrane dehydration and degassing method is also adopted at home and abroad, which is to make the oil entering the tank form a very thin oil film after passing through some degassing elements, and always complete the whole process of dehydration and degassing in the state of oil film, so that the water and gas in the oil can be easily removed

I. maintenance of transformer butterfly valve, throttle and oil plug:

1. Check whether the rotating shaft, baffle and other parts of the butterfly valve are complete, flexible and tight, and replace the sealing gasket. Through the 0.05Mpa oil pressure test, the baffle shall be closed tightly without serious leakage, the shaft rod shall be well sealed, and the "open" and "close" position marks shall be clear and correct

2. The throttle (emergency exhaust throttle and discharge throttle) shall be removed for disassembly and maintenance, and the sealing packing shall be grinded and replaced. After maintenance, a 0.15Mpa oil pressure test shall be conducted without leakage

3. Conduct comprehensive inspection on the air release plug, oil drain plug and oil sample accelerator of the transformer body and accessories, and replace the sealing gasket, which shall be well sealed without leakage

II. Treatment of transformer oil:

in order to improve the insulation strength, dielectric loss coefficient and other indicators of transformer oil, transformer oil must be treated before being injected into the oil tank to remove moisture, gas and impurities in the oil. In practical application, we have carried out targeted treatment for different types of transformer oil, and the effect is relatively good

1. For transformer oil that is generally polluted by impurities such as water and dust, a plate and frame pressure filter can be used. After multiple cycles of filtration, it can usually meet the requirements. Its principle is to use oil filter paper to absorb water and filter impurities. Because of its simple structure and convenient handling, it is also widely used. The disadvantage is that the filtration is not complete, the removal effect of fine impurities is not good, and the cost is relatively high. When the moisture is large, the oil filter paper needs to be replaced frequently

2. Now the vacuum oil filter is widely used, which can not only completely remove water and gas in the oil, but also effectively remove small impurities. The process flow is as follows: transformer oil to be treated → coarse filtration → fine filtration → vacuum dehydration and degassing of heating oil → oil purification. The coarse filter adopts metal filter and strong magnet, and the fine filter usually filters 1 ~ μ M minor impurities. At present, there are many kinds of fine filters, including metal powder sintered materials, metal microporous materials, ceramic filter materials and filter paper cores with special structures

transformer oil is heated, vacuumized, dewatered and degassed. The principle is to vacuum the oil tank, spray the heated transformer oil to form oil mist, and make the gas and water in the oil escape. The oil temperature is generally about 65 ℃, not too high to avoid aging the oil. This method has a good dehydration and degassing effect, and is a commonly used method at present. However, if the oil is sprayed into a very fine mist, it is easy to be pumped away by the vacuum pump

if the oil is sprayed into an oil bead with a certain diameter, it is difficult to give full play to the moisture and gas in the oil bead due to the high interfacial tension of the oil bead. For this reason, the diameter of the spray hole shall be properly selected, and several baffles shall be set at the evacuation port of the thermosetting plate of the tank to prevent the transformer oil from being pumped away by the vacuum pump

3. Treatment of contaminated transformer oil. Contaminated transformer oil (commonly known as dirty oil) refers to the transformer oil contaminated by colloid formed by the combination of extremely small impurities and oil molecules, as well as the transformer oil that has been used for many years. Generally, it is the oil released from repaired products (the pH value of this oil is very low). This kind of dirty oil must be treated by adsorption to improve its index. Generally, silica gel (SiO2) or activated alumina is used as adsorbent to display the value of the function of the experimental machine (A12O3). The design of the fixture in the waste oil treatment system is mainly based on the experimental standard of the material and the shape and material of the sample (especially the finished and semi-finished products). In order to ensure that the silica gel is in full contact with the transformer oil and facilitate the replacement of the silica gel, a number of diaphragms are set in the silica gel tank. The silica gel is loaded into a small cloth bag for rotation and cannot be loose. The heated transformer oil is sent to the silica gel tank for circulation for a certain period of time to give full play to the adsorption effect, and then injected into the clean oil tank through the oil filter. Regular monitoring shall be conducted during the treatment process to determine the adsorption effect. When the adsorption effect is not obvious, the silica gel shall be replaced. Generally, the amount of silica gel accounts for about 3% ~ 5% of the oil by weight. The waste oil treatment system shall be separated from the new oil treatment system to avoid cross contamination. Tanks and containers filled with used dirty oil must be thoroughly cleaned before they can be used in the oil system of normal production

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