Cast resin transformers are characterized by the conductors of the HV winding being embedded completely in an enclosed cast resin body with a smooth surface. Even if not specified so explicitly by the standard, this can be achieved in production of high voltage applications only using vacuum-encapsulated moulds.
These advantages make cast resin transformers a perfect choice for installations at places where safety is crucial, such as hospitals, public premises, airports, subway lines, mines, oil rigs, nuclear power plants, ships, etc. Cast resin transformers need only air for cooling.