Working of a Buchholz Relay
A Buchholz relay is a gas-actuated protection device used in oil-immersed transformers to detect faults like short circuits, inter-turn faults, and oil leaks. It operates based on the principle of gas accumulation and oil flow.
Working Principle
1. Gas Accumulation (Minor Faults)
When a minor internal fault occurs, it decomposes transformer oil, generating gas bubbles.
These gas bubbles accumulate in the relay's upper chamber, gradually lowering the oil level.
When the gas reaches a certain level, it tilts a float, which triggers an alarm signal.
2. Oil Flow (Severe Faults)
A severe internal fault (e.g., a short circuit) causes rapid gas generation and a sudden oil surge.
This high-velocity oil flow pushes a flap or float, activating the trip circuit to disconnect the transformer from the power supply.
Functions of a Buchholz Relay
Early Fault Detection: Provides an alarm before a
fault worsens.
Protection Against Major Faults: Triggers a trip
mechanism for serious internal issues.
Oil Leak Detection: Can indicate oil level
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