- Buchholz relay
In the field of electric power distribution and transmission, a Buchholz relay, also called a gas relay or a sudden pressure relay, is a safety device mounted on some oil-filled power
transformer s and reactors, equipped with an external overhead oil reservoir called a "conservator". The Buchholz Relay is used as a protective device sensitive to the effects of dielectric failure inside the equipment.The
relay has two different detection modes. On a slow accumulation of gas, due perhaps to slight overload, gas produced by decomposition of insulating oil accumulates in the top of the relay and forces the oil level down. A float operated switch in the relay is used to initiate an alarm signal. This same switch will also operate on low oil level, such as a slow oil leak.If an arc forms, gas accumulation is rapid, and oil flows rapidly into the conservator. This flow of oil operates a switch attached to a vane located in the path of the moving oil. This switch normally will operate a
circuit breaker to isolate the apparatus before the fault causes additional damage. Buchholz relays have a test port to allow the accumulated gas to be withdrawn for testing. Flammable gas found in the relay indicates some internal fault such as overheating orarcing , 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. The relay was first developed by Max Buchholz (1875-1956) in 1921 [ http://www.transformerworld.co.uk/buchholz.htm Tutorial T5, retrieved 2008 July 16 ] .
Names like "beechwood relay" or "beech relay" are a sign of a botched translation from German manuals.
References
External links
* [http://www.paradoxecorporation.com/Productos/EMB/buchholzrelaysenglish.PDF Buchholz relay technical specifications from Electromotoren und Gerätebau Barleben GmbH] Contains a detailed description (in English) of the Buchholz detection principles and mechanisms
* Koncar A.k.a Rade Koncar , Buchholz relays , for power and distribution transformers. [http://www.koncar-nsp.hr/eng/prikaz.asp?txt_id=1732]
* [http://www.pbpowereng.co.uk/pdf/PBSIWeir_Mk10%20Buchholz.pdf Buchholz Relay]
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