Transformer is an electrical device that transfers energy from one circuit to another by magnetic coupling with no moving parts. A transformer comprises two or more coupled windings or a single tapped winding and in most cases a magnetic core to concentrate magnetic flux. Water cooled transformers are cooled via a heavy-walled rectangular copper coolant tube that is in intimate contact with the secondary windings. Water cooled transformer is of different types one is oil immersed transformer having its core and coils immersed in oil, the cooling being effected by the natural circulation of oil over the water cooled surface. The water coiled surface is provided by water flowing through copper cooling coils immersed in the oil and located inside the main transformer tank, through which the oil flows by thermosiphon action. In water cooled transformer, the need for cooler stand by capacity is more important since a water cooled transformer has no naturally cooled capability and without standby a loss of cooling represents a loss of transformer.