Oil Treatment

Processing of transformer oil in most cases consists in their filtration, decontamination and dehydration. This can significantly improve the electrical properties of the oil. Do not forget that only thoroughly filtered and dry insulating liquid can be poured into power transformers. But even new oils are rarely so pure as to be suitable for pouring into high-voltage equipment. All because of pollution, falling into insulating liquids during their transport in transport barrels. In addition, in this case, it is also possible the interaction of oil with air, which contributes to watering.


Therefore, the treatment of insulating liquids should include the removal of such components:

  • particulate matter;
  • free and dissolved water;
  • dissolved air.

Filtration, degassing and dehydration can increase the breakdown voltage and improve the dielectric loss rate of transformer oil. As a result, electrical losses are reduced, the temperature of the oil decreases, and the service life of both the insulating liquid and the transformer itself increases. In fig. 1 shows the dependence of the characteristics of transformer oil on its moisture content.


Cleaning transformer oil is a preventive tool for servicing a transformer in order to prolong its life. Transformer oil can be completely cleaned and restored, make it as new. Due to the high cost of new oil, the following processing methods for transformer oil are used:


  • Centering processing. This method of treatment consists in removing moisture and mechanical particles from the oil when exposed to centrifugal force. It is possible to remove from the transformer oil only moisture, which is in a state of emulsion, and solid particles whose specific gravity is greater than the specific gravity of the transformer oil being processed. This cleaning method is used to prepare the oil for pouring into power transformers with voltage up to 35 kV;
  • Filtering treatment. Processing of transformer oil by filtering consists in passing it through porous partitions, on which the impurities present in it are retained;
  • Adsorption treatment. The process of purification of transformer oil using adsorption is based on the process of absorbing water and other impurities by various adsorbents. Basically, synthetic zeolites (minerals that tend to give up and absorb moisture) are used for this method. Processing of transformer oil using zeolites allows you to remove moisture from it, which is in a dissolved state;
  • Processing in vacuum installations. The main element in this process is the degasser. In the process of vacuum oil treatment, the raw transformer oil is heated to a temperature of 50-60 degrees and passes through all the steps of the degasser, after which it enters the transformer or container.


With good maintenance and processing of transformer oil, its life can be extended for an unlimited period.

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