Oil Immersed Hermetically Sealed Transformers

Oil Immersed Hermetically Sealed Transformers
The hermetically sealed oil transformers are usually manufactured with a sealed tank equipped with fin walls  that allow the expansion at the temperature variations. The tightness of the tank is up to 0.5 Bar. This type of  transformer is the most widely used one in the world. In the hermetically sealed transformers, the oil does not  contact with the air and its electrical properties are therefore not compromised ensuring a long life span of the  transformer. For powers exceeding 3150kVA,or in case of a transformer with radiators, the transformer can  still be hermetically sealed by means of a nitrogen cushion.

For this type of transformers the expansion of the insulating liquid is compensated by the elastic deformation  of the radiators cooling attached to the tank. The protection against internal faults is ensured by means of a  hermetical relay: Detection of Gas, Internal Over Pressure and Oil Over Temperature.