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The protective device that detects gas accumulation caused by internal faults is a Buchholz relay.
How it Works?
• Location: It is installed in the connecting pipe between the transformer’s main tank and the conservator tank.
• Gas Detection (Alarm): Minor or slow-developing internal faults (incipient faults) generate heat and decompose oil or insulation, producing gas. As this gas floats up toward the conservator, it gets trapped in the Buchholz relay, tilting an upper float switch to trigger an alarm.
• Oil Surge (Trip): Severe internal faults cause a sudden, violent surge of transformer oil, which pushes a lower float (or) baffle plate to send a trip signal and disconnect the transformer from the power supply.