Purpose of Purification Treatment of Transformer Oil
In order to ensure the quality of new oil and running oil, purification treatment is a common and important means. On the one hand, transformer oil can remove moisture, improve dielectric strength of insulating oil and demulsification degree of turbine oil, and reduce oil degradation rate. On the other hand, it can also remove mechanical impurity mixtures and sludge precipitation after oil degradation, so as to avoid blocking of oil system due to poor heat dissipation, which can prevent wear and tear of Mechanical impurity equipment.
2 Transformer Oil Pretreatment
The pretreatment methods of transformer oil are generally divided into sedimentation method, filtration method (pressure type and vacuum type) and centrifugal separation method.
Settlement method, also known as gravity settling method, is to remove impurities and water from oil by using the principle of gravity settling solid and liquid particles in turbid liquids. Precipitation method is simple and easy to purify without more and more complicated equipment. But this purification method is not thorough, it can only remove most of the water in the oil, and can naturally drop the mixture. Therefore, the general settlement method can only be used as pretreatment. The pretreated oil shortens the time, guarantees the product quality and reduces the purification cost.
2) Filtration method
Pressure filter paper filtration method, pressure filter method used by the equipment known as filter press, also known as frame plate oil filter. The pressure of gear pump is used to make the oil pass through the oil filter paper with the function of adsorption and filtration, remove the moisture, fine impurities and water-soluble acids in the transformer oil, and purify the transformer oil. The following problems should be paid attention to when using pressure oil filter.
滤纸在使用前应干燥，这样可以提高吸水率。同时，滤纸在烘烤时应特别小心，以免失火。如果变压器油中含有大量的水和杂质，应采用沉降法或离心滤油器进行处理，然后用压力滤油器进行过滤。在过滤过程中，应避免滤纸纤维被放入油中。油过滤开始后5 ~ 10min内，从滤油机中提取的油应重新导向油泵进口进行循环过滤。为了降低粘度，提高过滤速度和效率，应将油温提高到40 ~ 45℃。
The filter paper should be dried before use, so as to improve water absorption. At the same time, the filter paper should be carefully baked in order to avoid fire. If transformer oil contains a large amount of water and impurities, it should be treated by sedimentation method or centrifugal filter, and then filtered by pressure filter. In the process of filtration, filter paper fibers should be avoided from being put into oil. Within 5 to 10 minutes after the start of oil filtration, the oil extracted from the oil filter should be redirected to the inlet of the oil pump for cyclic filtration. In order to reduce the viscosity and improve the filtration speed and efficiency, the oil temperature should be raised to 40 - 45 C.
3) Vacuum filtration
Vacuum filtration is to extract trace water and gas from oil by atomizing transformer oil under high vacuum and low temperature. Because vacuum filters also have filters, they can remove some solid impurities. It is not only more economical than pressure filtration, but also has higher purification degree and efficiency. It can remove trace moisture in oil, maximize the strength of insulating oil and reduce fuel consumption. When the flash point of transformer oil decreases due to faults and flammable gas precipitates, the flash point can be recovered by vacuum purification.
4) Centrifugal method
Centrifugal separation is the use of oil, water and impurities in the density of the three, centrifugal force in the centrifuge rotation of the separation and purification effect. Oil is the lightest, concentrated in the center of the rotary drum, and the density of water is enough to remain in the outer layer of the oil. The solid impurities in transformer oil reside most seriously in the outer layer, which achieves the purpose of separation and purification. This method has high crude oil purification efficiency. As long as the oil contains more water and mechanical impurities, it can be used. Especially for the removal of slag, carbon particles and other impurities in oil, but this method has its limitations and can only be used to remove impurities with higher density than oil.