What is transformer oil and what functions does it perform?

Transformer oil is an insulating fluid used mainly in oil immersed transformers. Its primary functions are electrical insulation and heat removal. It fills spaces around windings and core to increase dielectric strength and reduce partial discharge risk. It also transfers heat to radiators or coolers for dissipation. In addition, oil can help suppress arcing, protect cellulose insulation from oxygen, and carry dissolved gases that serve as diagnostic indicators in DGA programs. Oil quality directly affects transformer reliability and life.