How can I tell if the transformer pressure relief valve is working properly?

I. Appearance and sealing inspection

1. Visual inspection of appearance
   • ferret outpressure relief valveWhether the shell has deformation, cracks, damage or corrosion, whether the injection port is blocked by foreign objects (such as oil, dust, metal debris, etc.), if blocked may lead to the valve can not be opened or closed properly.
   • Check whether the sealing rubber gasket is aging and broken, and whether there are traces of oil seepage at the interface (oil seepage may lead to internal pressure leakage, affecting the precision of valve operation).
2. Confirmation of signal pole status
   • Pressure relief valves are normally equipped with a mechanical signaling lever (or indicator) that should normally be in the reset position (e.g., vertical or in a specific marked position). If the signaling lever is abnormally raised or shifted, it may indicate that the valve has been actuated (a history is required to determine if this is a false operation).

Second, action signal and electrical function test

1. Microswitch and Signal Loop Detection
   • The microswitch inside the pressure relief valve is used to trigger an alarm or trip signal when the valve is actuated. It can be tested in the following ways:
     • Push the membrane plate manually (under the premise of power failure and ensuring safety), simulate the state of pressure rise, observe whether the micro switch is activated, whether the signal circuit (such as contacts in the junction box) is open, and whether the corresponding monitoring system receives an alarm signal.
     • Measure the insulation resistance of the microswitch contacts with a multimeter (reference standard: insulation resistance should be ≥ 10MΩ), if the resistance value is too low, there may be a contact short circuit or moisture problem.
2. Signal Transmission Verification
   • Check the signal cable for breakage and poor contact to ensure that the signal transmission from the pressure relief valve to the transformer control cabinet is normal (you can test whether the signal is accurately uploaded to the monitoring system by simulating the action).

III. Pressure test and action performance verification

1. Opening pressure and closing pressure test
   • Test Methods: According to JB/T 7065 - 2023 standard, use special pressure test device (such as pneumatic or hydraulic pump) to apply slowly increasing pressure to the valve, record the pressure value when the valve is opened (opening pressure) and the pressure value when the valve is closed after the pressure decreases (closing pressure).
   • standardized requirements::
     • The opening pressure should be in accordance with the design value (usually 0.05~0.15MPa, specific to the transformer manufacturer's parameters prevail), allowable deviation ±10%.
     • The closing pressure is generally 70%~80% of the opening pressure. If the closing pressure is too low, it may lead to frequent opening of the valve or poor sealing.
2. Open time test
   • At the rated opening pressure, measure the time from triggering to full opening of the valve (ideally it should open quickly within 2ms), if the opening time is too long, it may affect the efficiency of pressure relief in case of failure.

IV. Operational status monitoring and anomaly detection

1. Oil Chromatography Aids Judgment
   • If a fault occurs within the transformer (e.g. turn-to-turn short-circuit), the decomposition of the insulating oil produces gases which may cause the pressure relief valve to operate. The reasonableness of the pressure relief valve action can be indirectly verified by oil chromatography analysis (e.g. detection of H₂, CH₄, C₂H₂ and other gases) to determine whether there is an abnormal overheating or discharge fault within the transformer.
2. Operating noise and pressure fluctuation monitoring
   • During normal operation, the pressure relief valve should have no abnormal sound. If you hear vibration inside the valve or oil seepage from the injection port, the internal spring may have failed or the membrane disk may have a bad seal.
   • In conjunction with transformer oil temperature, oil level, and pressure sensor data (if available), observe for pressure surges with no apparent cause (may indicate valve malfunction or internal failure).

V. Periodic maintenance and functional test cycles

• routine inspectionAt least once a month, focusing on the appearance, condition of the signaling rod and oil seepage.
• Functionality test: Conduct opening pressure, closing pressure and signaling circuit test once every 1~2 years (refer to "Fujian Electric Power Testing and Research Institute Transformer Pressure Relief Valve Test Operation Guideline").
• Inspection during overhaul: When transformers are overhauled, pressure relief valves are disassembled, internal parts (e.g., springs, membrane disks) are cleaned, deteriorated rubber gaskets are replaced, and a full pressure test is performed.

VI. Common abnormalities and treatment measures

summarize