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Once energized, a transformer produces a humming sound due to high-voltage magnetic flux. During normal operation, this sound is uniform. If abnormal noises arise, the causes should be identified and addressed promptly.
1.Increased Noise Levels
If the noise intensifies but remains uniform, potential causes include:
Overvoltage in the Grid: This may occur due to single-phase grounding or resonance overvoltage. Verify by cross-checking with the voltage meter readings.
Overload: Overloading causes a heavy "buzzing" sound. If the transformer load exceeds permissible limits, reduce it as per operational procedures.
Solution: Analyze the cause, document the event, monitor closely, and restore normal operations as soon as possible. If caused by overload, handle according to overload management protocols.
This might result from loose components causing vibrations. If accompanied by increased noise without significant current or voltage anomalies, it could indicate loose internal clamping or core bolts.
Solution: If it doesn’t affect operation, monitor closely, record the issue, and report to supervisors for a scheduled inspection.
Discharge sounds, often observed with visible blue corona or sparks near bushings, suggest severe pollution or loose connections. Internal discharges may stem from static or inter-turn discharges or poor tap changer contact.
Solution: Report to supervisors and request an outage for inspection.
Explosive sounds indicate insulation breakdown. The transformer should be taken offline immediately for inspection.
Boiling noises, coupled with abrupt temperature increases and oil level rises, typically signal a winding short circuit or overheating due to poor tap changer contact. Shut down the transformer immediately for inspection.
Monitoring the top-oil temperature helps control winding temperature to prevent insulation degradation. If the temperature rises 10°C above normal under consistent load and cooling conditions, and cooling systems and thermometers are confirmed functional, the issue likely stems from internal faults like core heating or inter-turn short circuits.
Solution: Shut down the transformer immediately to prevent further damage.
Transformer oil should be bright yellow and transparent. Any sudden deterioration in color or the presence of carbon deposits indicates internal issues.
Solution: Collect an oil sample for analysis and halt operation for inspection if necessary.
Oil level indicators display acceptable levels for temperatures of -30°C, +20°C, and +40°C. Deviations can indicate issues:
1.High Oil Level: Inspect for normal load and temperature. If these are normal, check for a blocked breather or gauge pipe.
Solution: Adjust gas protection settings temporarily, clear blockages, or drain excess oil.
2.Low Oil Level: This may activate gas protection and expose cores and windings to air, causing insulation failure.
Solution: Refill oil using a vacuum injection method or halt operation for repairs if leakage is severe.
Overload is evident when the current exceeds stable levels, triggering alarms.
Solution: Adjust operation modes, activate standby transformers, and redistribute load. Monitor oil levels and temperatures to ensure they remain within permissible limits.
Cooling system issues may include faults in oil pumps or water systems.
Solution: Activate standby coolers, restore cooling functionality, or lower the load to prevent overheating.
Causes of activation include minor internal faults, air intrusion, oil level drops, or secondary circuit malfunctions.
Solution: Conduct external inspections and gas sampling for chromatographic analysis to determine the cause.
Common overheating causes include:
Solution: Monitor temperature, analyze the cause, and conduct repairs during an outage if needed.
Per DL/T572-95 "Electric Power Transformer Operating Code," transformers must be shut down if:
1.Noise significantly intensifies with explosive sounds.
2.Severe oil leakage reduces oil below indicator limits.
3.Bushings exhibit severe damage or discharge.
4.Transformer smokes or catches fire.
Following an automatic trip, perform systematic checks:
Confirm which protection systems activated and their accuracy.
Check for system faults and their nature.
Solution: If safe, test re-energization for minor issues, but investigate thoroughly for major protection activations like differential or gas protection.
Collect relay gas samples for analysis, inspect oil levels, colors, and any structural deformations.
Solution: Address the identified issue before re-energization.
Inspect for short circuits, damaged equipment, and protection activations in downstream systems.
Solution: After isolating the fault, restore power systematically.
Inspect all components within the differential protection range.
Solution: Conduct thorough diagnostics before re-energizing.
Handle fires using the "Shutdown—Drain Oil—Extinguish" principle:
1.De-energize affected circuits.
2.Drain oil below the fire level unless the fire originates internally.
3.Use firefighting equipment such as CO2, dry powder, or sand.
Precaution: Ensure personnel safety and involve fire services as necessary.
