What is Buchholz Relay?

Actually, any types of relay is used to protection purpose but the main objective of a relay is to sense the excess current flow in the circuit and depends upon the intensity of the current flow the relay trips and the circuit breaker is closed. Therefore the faulted part of the circuit is isolated from the healthy network. Now Buchhloz's relay is a special type of relay which is used only in the transformer tanks and unlike being activated by the excess current voltage, it trips by the gases formed. Whenever any fault take place in the transformer, the oil decomposes and various chemical reactions take place and several gases are formed. Using the intensity of gas production, Buchholz's relay operated. There are two hinged flow situated in the middle chamber. The lower one is connected with the circuit breaker and the upper one initiates a signal or alarm.

When the fault is minor, the rate of production of gas is low and therefore the force induced by them is also low which don’t tilt the lower hing but stored in the upper part of the chamber. As soon as the amount of the gases increased, it tilts the upper hing which initiates a signal and the alarm goes off, which indicates that there is something wrong in the transformer. But when the fault is severe the rate of production of gas is pretty high which is able to tilt the lower hing and as a result the contacts of the circuit breaker is closed and the transformer circuit is tripped.