Buchholz relay

Categories: Technology stubs | Transformers (electrical)

A Buchholz relay, also called gas relay, is a safety device mounted on some oil-filled power transformers and choke coils, equipped with an external overhead oil reservoir called a conservator.The Buchholz Relay is used on conservator type oil preservation systems as a protective device sensitive to events which occurs during dielectric failure inside the transformer When an electric arc or overheating develops inside the transformer coils, gas is generated. The relay has two different detection modes. On a slow accumulation of gas, due perhaps to slight overload, the relay generates an alarm signal. If an arc forms, gas accumulation is rapid, and oil flows rapidly into the conservator. The relay will operate a circuit breaker to shut down the apparatus before the fault causes additional damage. Buchholz relays have a test port to allow accumulated gas to be withdrawn for testing. Flammable gas found in the relay indicates some internal fault, whereas air found in the relay may only indicate low oil level or a leak. Buchholz relays have been applied to large power transformers at least since the 1940's.

Names like beechwood relay or beech relay are a sign of a botched translation from German manuals.