What Are the Handling Procedures After Transformer Gas (Buchholz) Protection Activation?
What Are the Handling Procedures After Transformer Gas (Buchholz) Protection Activation?
When the transformer gas (Buchholz) protection device operates, a thorough inspection, careful analysis, and accurate judgment must be carried out immediately, followed by appropriate corrective actions.
1. When the Gas Protection Alarm Signal is Activated
Upon activation of the gas protection alarm, the transformer should be inspected immediately to determine the cause of operation. Check whether it was caused by:
Accumulated air,
Low oil level,
Secondary circuit faults, or
Internal faults in the transformer.
If gas is present in the relay, the following actions should be taken:
Record the volume of gas collected;
Observe the color and odor of the gas;
Test whether the gas is combustible;
Take gas and oil samples for dissolved gas analysis (DGA) using gas chromatography.
Gas chromatography involves analyzing the collected gas using a chromatograph to identify and quantify key components such as hydrogen (H₂), oxygen (O₂), carbon monoxide (CO), carbon dioxide (CO₂), methane (CH₄), ethane (C₂H₆), ethylene (C₂H₄), and acetylene (C₂H₂). Based on the types and concentrations of these gases, the nature, development trend, and severity of the fault can be accurately determined in accordance with relevant standards and guidelines (e.g., IEC 60599, IEEE C57.104).
If the gas in the relay is colorless, odorless, and non-flammable, and chromatographic analysis confirms it to be air, the transformer may continue operating. However, the source of air ingress (e.g., poor sealing, incomplete degassing) must be identified and rectified promptly.
If the gas is combustible and the dissolved gas analysis (DGA) results from the oil sample show abnormalities, a comprehensive assessment must be conducted to determine whether the transformer should be taken out of service.
2. When the Gas Relay Causes a Trip (Power Off)
If the Buchholz relay has triggered a trip and disconnected the transformer, the unit must not be re-energized until the root cause has been identified and the fault fully eliminated.
To determine the cause, the following factors should be carefully evaluated and analyzed collectively:
Was there restricted breathing or incomplete air degassing in the conservator tank?
Is the protection system and DC secondary circuit functioning normally?
Are there any visible external abnormalities on the transformer that reflect the nature of the fault (e.g., oil leakage, bulging tank, arcing marks)?
Is the gas accumulated in the gas relay combustible?
What are the results of the chromatographic analysis of both the relay gas and dissolved gases in the oil?
Are there any results from additional diagnostic tests (e.g., insulation resistance, turns ratio, winding resistance)?
Did any other transformer relay protection devices operate (e.g., differential protection, overcurrent protection)?
Conclusion
Proper response to Buchholz relay activation is critical for ensuring transformer safety and power system reliability. Immediate inspection, gas analysis, and comprehensive fault diagnosis are essential to distinguish between minor issues (e.g., air ingress) and serious internal faults (e.g., arcing, overheating). Only after a thorough evaluation should decisions be made regarding continued operation or shutdown for maintenance.
