What is Buchholz Relay?

Basically Buchholz relay is used to detect internal faults in oil filled transformers. And that oil is used as insulation for the transformer body. This relay works on the principle of gas detection. and is also known as a safety device used in oil-filled transformers. When internal faults occur inside, the current goes up to a very high abnormal range. This high current automatically increases the operating temperature inside. As the oil is filled in, the excess heat generated causes it to evaporate. As it begins to change to gaseous form, it rises to the oil reservoir.

A Buchholz relay is placed between the protector and the transformer tank (body). It detects this gas and immediately trips the circuit. This means the transformer is closed for operation, thereby avoiding any untoward incident.