What is Buchholz relay in Transformer? How does it work?

Buchholz relay is used for the protection of transformers from the faults occurring inside the transformer.

Short circuit faults such as inter turn faults, incipient winding faults, and core faults may occur due to the impulse breakdown of the insulating oil or simply the transformer oil.

What is a Buchholz relay?

Buchholz relay is a type of oil and gas actuated protection relay universally used on all oil immersed transformers having rating more than 500 kVA.

Buchholz relay is not provided in relays having rating below 500 kVA from the point of view of economic considerations.

Why it is used in transformers?

This relay is used for the protection of transformers from the faults occurring inside the transformer.

Short circuit faults such as inter turn faults, incipient winding faults, and core faults may occur due to the impulse breakdown of the insulating oil or simply the transformer oil. It will sense such faults and closes the alarm circuit.

Buchholz Relay
Buchholz Relay working Principle
Working principle

It relies on the fact that an electrical fault inside the transformer tank caused by the generation of gas. And if the fault is high enough, it will be accompanied by a surge of oil from the tank to the conservator

Read also: Power Transformer MCQs

Whenever a fault occurs inside the transformer, the oil in the transformer tank gets overheated and generates gases. The generation of the gases depends mainly on the intensity of fault produced inside the transformer.

The heat generated during the fault will be high enough to decompose the transformer oil. As a result of this, the gases produced detect the winding faults. This is the basic principle behind the working of the Buchholz relay that we need to understand for the understanding of protections of transformers.

Asif Malik

A young Electrical Engineer having more than 5 years of experience in Electrical Power System, Construction and Execution of different projects, Project Management, Electrical Inspection. He is a article Writer as well on the different topic related to Electrical Engineering and Information Technology.

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