Buchholz relays in South Africa
by P de Matos, Allbro
Published in: Transformers and Substations Handbook: 2014
Chapter 1: Design and manufacture of transformers - page 24
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After basic thermal protection and pressure relief devices, Buchholz relays are traditionally the most commonly used protection devices on oil-filled distribution and power transformers.
Categorised as Asset Protection Devices, Buchholz relays are used in oil-filled power and distribution transformers. Normally installed in the pipework, between the main transformer tank and the conservator, Buchholz relays perform three primary functions as protection devices:
o Monitoring gas build-up caused by the degradation or decomposition of the solid/liquid insulation owing to overheating or arcing
o Monitoring of oil surge caused by arcing or short-circuit conditions in the transformer
o Monitoring oil loss in the conservator
During normal transformer operating conditions, the Buchholz relay is filled with oil when installed in the pipework between the main tank and the conservator.
The gas-build-up (or loss of oil) function is tested by slowly introducing air into the gas sampling valve and recording at which volume the alarm and then the trip switches are activated.
- Buchholz relays monitor gas build-up caused by the degradation or decomposition of the solid/liquid insulation owing to overheating or arcing.
- Buchholz relays monitor oil surge caused by arcing or short-circuit condition in the transformer.
- Buchholz relays monitor oil loss in the conservator.