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Test and Purification Methods Used For Transformer Oil Filtration

Transformer oil is mineral insulating oil that is derived from crude petroleum. Transformer oil is a combination of various hydrocarbons. If the transformer oil is of good quality, it should insulate and prevent flash over of the exposed parts inside the equipment and effectively transformer the heat from the core to the radiating surface. There are many tests to check the quality of transformer oil. Filtration process is among specialized methods that treat transformer oil and offer contamination free transformer oil for use.

Test Purification Methods For Transformer Oil Filtration

Transformer oil treatment

You can take help of centrifugal separators to remove finely divided solid content and make water free from oil. However, vacuum edge type filers can be used for treating transformer oil. The process of filtration involves combination of processes, including filtration, dehydration, and de-aeration.

Direct purification of oil is used in switch gear and small transformers. The filter plant is used to remove dirt from oil, clean the equipment and fill the purified oil inside the transformer. All the purification of contaminated oil is done outside. When it comes to large transformers, oil is distributed through the purifying plant, and it is being taken out from the bottom and re-poured at the top.


Inhibiting oil implies making an addition of substance to delay oxidation. People use inhibitors usually in both new and used transformer oil. DBPC or Ditertiary Butyl Para Cresol is commonly used as inhibitor, in 2.5:3 parts/ 1000 parts of oil by weight. You can mix the new oils with each other if they satisfy the same standard specifications shared by experts. You can mix inhibited oils with un-inhibited oils.

Test Purification Methods For Transformer Oil Filtration

The list of tests perform by professionals for transformer oil are:

  • Dielectric strength
  • Water content
  • Interfacial tension
  • Neutralisation value
  • Dielectric dissipation factor test for corrosive sulphur in oil
  • Specific resistance
  • Test for oxidation stability
  • Pour point
  • Viscosity
  • Flash point
  • Sludge test
  • DGA (Dissolved Gas Analysis)

Call experts of Royal Transformers today to avail comprehensive testing and maintenance services for transformers. They offer transformer oil filtration services and solutions, repairing and maintenance facilities at minimum costs.