The Buchholz relay is a protective device used in electrical power transformers to detect and prevent internal faults, such as overheating or insulation breakdown. It is named after its inventor, Max Buchholz, a German engineer who patented it in 1921. The Buchholz relay is typically installed in the oil-filled conservator tank of a power transformer.

What is a function of Buchholz relay?

The primary function of the Buchholz relay is to provide early warning and protection against faults that can occur within the transformer. It operates based on the principle that certain types of faults in a transformer, such as an internal short circuit or partial discharges, can generate gas and oil flow disturbances within the transformer tank. The Buchholz relay is designed to detect these gas and oil flow disturbances and activate an alarm or trip signal to disconnect the transformer from the power source, thereby preventing further damage.

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.

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.

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