Answer / sanskar

Difference between Buchholz Relay and Oil Surge Realy:
Generally there is confusion between operation of Buchholz relay and Oil surge relay.

So, Let me interpret the major differences between them.

Buchholz Relay
Oil Surge Realy
Buchholz relay is used for protection of oil filled transformers/reactors fitted with conservators against low oil level and internal faults.
OSR is used to report any malfunction developed inside the On Load Tap Changer Chamber.
Buchholz relay is Gas actuated Relay.
OSR is Oil actuated Relay.
Buchholz relay should be mounted in the connecting pipe between the transformer and conservator tank.
OSR is installed in the pipe between OLTC head and the oil conservator.
Buchholz relay is actuated by the gases flowing through and accumulated in relay.
OSR relay is actuated when the flow rate of oil exceeds the preset value.
Buchholz relay detects the fall in oil level due to formation of gases after any internal fault inside the transformer.
OSR detects excessive oil surge after any fault occurs inside OLTC Chamber.

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