Is part of the insulation system and serves as a cooling medium in the transformer, this oil can be regenerated to recover its properties allowing to extend the life expectancy and reliability of the transformer.
Dielectric mineral oil

Dielectric mineral oil
It is a compound derivate from the isoparaffinic, naphthenic and aromatic hydrocarbons, which is obtained by distillation and refining processes, to have suitable properties as insulating medium, coolant, compatible with other parts of the transformer and stability to oxidation processes.