Buchholz Relay Protection of Power Transformer

Author

Bagul Roshan Pandurang and Dhanshri Shantaram Dhanwate

Abstract

 Power transformers are among the costliest and most important elements of a power system, and an internal fault can cause long outages, fire and heavy financial loss. Electrical relays such as differential and overcurrent relays respond to current, but many faults inside an oil-filled transformer first appear as gas generation and oil movement. The Buchholz relay is a gas-operated mechanical relay fitted in the pipe between the main tank and the conservator to detect exactly these effects. This paper presents the need for transformer protection, the construction of the relay, its two-stage working principle (alarm on slow gas accumulation and trip on oil surge), installation requirements, gas analysis for fault diagnosis, testing and maintenance, and a comparison with other protective devices. A mathematical description of gas accumulation and oil-surge detection, an operating-logic flowchart, an alarm and trip circuit, and a test plan for a polytechnic laboratory are also given. The paper concludes that the Buchholz relay, used together with differential protection and dissolved gas analysis, remains an essential, economical and reliable protection for oil-immersed transformers.

Keywords

Buchholz relay, power transformer, gas-operated relay, transformer protection, incipient fault, conservator, dissolved gas analysis, oil surge.

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References

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