Dec 9, 2013

Buchholz Relay Principle and Operation

 Buchholz Relay
An illustration of a buchholz relay device is shown in figure. A buchholz relay is a protective device for scrutiny the gas and oil actions in oil immersed transformers. It’s used on much all power transformers with the exception of tiny distribution sizes. In observe it's proved to be the sole protecting device that may clear bound varieties of faults. The buchholz relay depends on the principle that in fault conditions, gas is generated within the transformer tank from the insulating oil.
The buchholz relay is positioned within the pipe work between the transformer and its conservator as shown below, and is stuffed with oil throughout traditional transformer operation.  
buchholz relay function

The interior mechanism of a buchholz relay in the main contains 2 floats and is schematic arrangement shown below. Throughout traditional operation, the relay is totally stuffed with oil keeping the floats in their high limit or rest position. The contact mechanisms within the relays respond to:
 Buchholz Relay Function
  • Slight faults inflicting a slow evolution of gas within the transformer.
  • Serious faults making an on the spot surge of oil (e.g. short circuits etc.)
  • Oil outflow

Operation Of Buchholz Relay

When a small fault happens within the power transformer, the little bubbles of gas that pass upwards towards the oil conservator tank are cornered within the relay housing this inflicting its oil level to fall. As a consequence, the higher float drops and actuates the external alarm switch. If gas carries on to be generated then the second float operates the second switch that's normally accustomed isolate (trip) the transformer.

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