What is the function of the buchholz relay in a transformer？

Revised and Polished Version:

The Buchholz relay is a critical protective device used in oil-immersed transformers, serving multiple key functions to ensure safe and reliable operation:

1. Monitoring Oil Level Changes:

The relay continuously monitors the oil level within the transformer tank. A drop in oil level—often caused by leaks or oil loss—can compromise the transformer’s insulation and cooling capabilities, potentially leading to overheating or insulation failure. The Buchholz relay detects such changes and initiates appropriate alarm or shutdown actions.

2. Detecting Gas Accumulation:

Under abnormal operating conditions, such as insulation aging, localized overheating, or partial discharges, insulating materials and transformer oil may decompose and generate gases like hydrogen, methane, ethylene, and acetylene. The Buchholz relay detects the accumulation of these fault-generated gases in the oil, providing an early indication of developing internal problems.

3. Identifying Internal Faults:

In the event of serious internal faults—such as winding insulation breakdown, arcing, or severe short circuits—rapid gas generation occurs, often accompanied by a surge of oil flow. The Buchholz relay is designed to sense both the slow accumulation of gases (for minor faults) and sudden oil displacement (for major faults), triggering alarm signals for minor issues and initiating immediate tripping of the transformer for severe faults.

4. Providing Protective Actions:

Upon detecting abnormal conditions, the Buchholz relay activates protective measures. It typically has two sets of contacts: one for alarm (activated by gas accumulation) and another for tripping (activated by sudden oil flow due to major faults). This dual-stage response helps prevent catastrophic damage and enhances system safety.

Conclusion:

In summary, the Buchholz relay plays a vital role in the early detection of incipient faults within oil-immersed transformers. By monitoring oil levels and gas formation, it enables timely intervention, minimizes damage, and significantly improves the reliability and longevity of the transformer. As such, it is an indispensable safety component in power transformer protection systems.