Transformer oil filtration
Transformer oil is used in oil-filled transformers because it has excellent electric insulating properties. The stability at high temperatures is very good. Usually it is a highly refined mineral oil.
Its function is to insulate and suppress arching and corona. The oil also serve as a coolant in the transformer.
A transformer filter is designed to degas the oil and remove moisture raised. This is accomplished with low pressure and at a temperature of about 70 degrees Celsius. The machine also filters the oil to get rid of particles.