Why Pressure Relief Device(PRD) for Oil Filled Transformer?

Winding of the transformer is housed in the transformer oil tank. The oil is used in the oil filled transformer for insulation as well as for cooling purpose. In case of the fault inside the transformer caused by sudden and severe short circuit , the transformer oil gets heated up and enormous gases are evolved in the transformer tank which cause substantial increase in the internal pressure develops the pressure in the transformer tank. If the increased pressure is not vented outside of the transformer tank there may be potential hazard of transformer tank explosion. in this case, PRD of transformer is used to protect the transformer.

The transformer tank is not designed to sustain pressure as it is not considered as a pressure vessel, and if the gas pressure is not vented outside of the transformer tank, the tank can explode. Therefore, to release the excess pressure of transformer tank pressure relief device or PRD of transformer is installed for oil filled transformer to protect the transformer under severe fault condition.

A Pressure Relief device (PRD of Transformer) is also called Pressure Relief Valve(PRV). A  (PRV) is a type of valve used to release stored gas in various equipment in order to maintain an optimal pressure level. PRV opens gradually as pressure builds up in order to release the necessary amount of pressure.