It is installed in the pipe connecting the transformer tank to the conservator.
When a fault occurs inside the transformer, it can generate gas, which accumulates in the relay. The presence of gas in the Buchholz relay is a strong indicator of an internal fault, and the type and quantity of gas can provide clues about the nature of the fault.
Common Causes of Gas Accumulation in the Buchholz Relay:
1. Insulation Breakdown:
- Faults such as short circuits or arcing between windings or between windings and the core can cause insulation to break down, producing gases like hydrogen (H₂), methane (CH₄), and acetylene (C₂H₂).
2. Overheating:
- Localized overheating due to poor connections, overloading, or circulating currents can decompose the transformer oil, generating gases such as methane (CH₄) and ethylene (C₂H₄).
3. Core Faults:
- Faults in the core, such as shorted laminations, can cause localized heating and gas generation.
4. Partial Discharge:
- Partial discharges within the transformer can produce hydrogen (H₂) and small amounts of methane (CH₄).
5. Oil Degradation:
- Aging or contamination of the transformer oil can lead to gas formation even without a major fault.
Actions to Take When Gas Accumulates in the Buchholz Relay:
1. Alarm Stage:
- If the gas accumulation is small, the Buchholz relay will typically trigger an alarm. The transformer should be inspected, and a gas sample should be taken for analysis (Dissolved Gas Analysis or DGA) to determine the cause.
2. Trip Stage:
- If the gas accumulation is significant, the relay may trip the transformer to prevent further damage. Immediate investigation and repair are required.
3. Gas Analysis:
- Perform a DGA to identify the types and concentrations of gases. This helps diagnose the fault type (e.g., thermal, electrical, or corona discharge).
4. Inspection and Repair:
- Inspect the transformer internally to locate and repair the fault. This may involve rewinding, repairing insulation, or replacing damaged components.
5. Preventive Measures:
- After repair, ensure proper maintenance, monitor loading conditions, and perform regular oil testing to prevent future faults.
Common Gases and Their Significance:
- Hydrogen (H₂): Indicates partial discharge or arcing.
- Methane (CH₄): Suggests overheating or oil degradation.
- Acetylene (C₂H₂): Indicates high-energy arcing or severe faults.
- Ethylene (C₂H₄): Associated with thermal faults.
- Carbon Monoxide (CO) and Carbon Dioxide (CO₂): Indicate cellulose (paper) insulation degradation.
If gas accumulation is detected, it is critical to act promptly to prevent further damage to the transformer and ensure the reliability of the power system.
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