How to deal with the moisture in transformer insulating oil?
2020/1/5??????view:
On the one hand, the purification of transformer oil can remove water, improve the insulation strength of transformer oil, reduce the degradation speed of transformer oil quality, on the other hand, it can also remove the sludge sediment generated after the degradation of transformer oil, avoiding the possibility of poor heat dissipation.
The gas, moisture and solid particles in transformer oil can be reduced to meet the requirements of relevant indexes of transformer oil only by physical separation process. Purification methods include mechanical filtration, centrifugal separation and vacuum filtration. In use, it should be selected according to the requirements of the indicators that the transformer oil purification should reach and the characteristics of the treatment methods.
1、 Mechanical filtration equipment can not effectively remove dissolved or colloidal impurities in transformer oil, nor can it remove gas. Pay attention to the following items when using:
1. The filter medium of the filter shall be fully dry before use. When filtering the transformer oil containing water, it should be filtered at a lower temperature (generally lower than 45 ℃), which is conducive to the improvement of dehydration effect.
2. The working condition of the oil filter mainly depends on the observation of the oil pressure at the inlet of the oil filter and the determination of the moisture content or breakdown voltage value of the oil at the outlet of the oil filter. When it is found that the oil pressure of the filter increases, or the moisture content of the filtered oil increases, and the breakdown voltage decreases, measures such as replacing the filter paper should be taken.
3. When the filter contains more sludge or other solid impurities, the number of times to change the filter paper shall be increased. If necessary, pre filtration device (filter screen) can be used.
4. In the treatment of UHV Transformer oil, mechanical filtration and vacuum filtration can be used together.
2、 When dealing with transformer oil containing a large amount of water, solid particles, oil sludge and other suspended solids, centrifugal separation must be used for purification first.
Centrifugal separation requires that the speed should be greater than 5000r / min. It can remove the pollutants with high concentration, but it can't remove the dissolved water in transformer oil. It can only be used as a kind of primary filter treatment for transformer oil with high concentration pollutant.
3、 Vacuum filtration is suitable for deep degassing and dehydration of transformer oil. The following precautions shall be taken when using vacuum filtration:
1. It is better to remove oil sludge and free water by cold mechanical filtration, while it is better to remove dissolved water and suspended water by hot vacuum treatment.
2. The oil temperature shall be controlled below 70 ℃ to prevent oil oxidation or loss of T501 and some light components in transformer oil.
3. Before vacuum treatment, centrifugal separation or mechanical filtration should be used to improve the purification efficiency of transformer oil.
4. When the ultra-high pressure transformer oil is deeply dehydrated and degassed, a two-stage vacuum oil filter shall be used, and the vacuum degree shall be kept below 133pa.
5. In the process of vacuum filtration, the air content, moisture content or breakdown voltage of the inlet and outlet oil of the oil filter shall be measured regularly to supervise the purification efficiency of the oil filter.
4、 When the electrical equipment needs to be refilled, it shall be purified again, and then directly injected into the equipment. This direct purification method has been widely used in switches and small transformers. However, care shall be taken to ensure that the core winding, inner barrel and other oil-bearing partition board shall be cleaned with purified transformer oil.
5、 There are two ways of Circulation Purification: direct circulation purification and indirect circulation purification. The indirect circulation method is usually used.
a) Direct circulation purification is to connect the oil filter and the transformer equipment into a circulation circuit. Through the oil purifier, the transformer oil is extracted from the bottom of the electrical equipment and returned from the top of the electrical equipment. The returned transformer oil shall be returned smoothly and horizontally near the top oil level to avoid mixing the treated transformer oil with the transformer oil that has not been treated by the oil purifier.
b) Indirect circulation purification is to connect the oil filter in series between the equipment and the tank for transformer oil treatment, filter the transformer oil in the equipment first and then send it to the tank, and then pump the treated transformer oil back to the equipment after removing the moisture and gas from the internal workpiece of the equipment. When the indirect circulation method can not be implemented (such as when the transformer shell can not bear vacuum), the direct circulation method shall be adopted.
6、 In special cases, when the electrical equipment cannot be cut off but it is necessary to filter the oil with electricity, safety measures shall be taken in all aspects, and special attention shall be paid to:
- the inlet and outlet pipelines of the oil filter must be tight to avoid air inlet and oil leakage of the pipeline system, so as to avoid failure;
- control the oil flow speed not to be too large, so as to avoid danger caused by flow electrification.
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