Is Forced Re-energization Allowed After Internal Fault Tripping of Oil-Immersed Transformers?

Forced re-energization is strictly prohibited when an oil-immersed transformer trips due to confirmed internal faults.Internal failures include winding short circuits,insulation breakdown,core damage,internal arcing and oil deterioration.Forced power restoration will intensify faults,cause insulation burnout,tank rupture,oil ignition or even explosion,resulting in permanent equipment scrapping and serious safety accidents.

1.Why Forced Re-energization Is Dangerous

Internal faults leave residual defects inside the transformer.Arcing generated during faults will produce carbon particles,combustible gas and damaged insulation materials.If power is restored without troubleshooting,the existing defects will reignite electric arcs,expand the fault scope,and trigger more severe short circuits.Meanwhile,combustible gas accumulated in the oil tank may explode under electric impact.

2.Standard On-Site Handling Procedures

2.1 Lockout and Site Protection

Immediately perform lockout-tagout after tripping,hang warning signs and isolate the equipment.Do not remove protection signals or reset trip relays arbitrarily.Keep personnel away to prevent fire or gas leakage hazards.

2.2 Preliminary Fault Judgment

Check the action status of gas relays,differential protection,overcurrent protection and temperature protection.Observe oil level,oil color,gas composition,abnormal noise and oil leakage.Collect fault records to preliminarily determine the fault type and location.

2.3 Comprehensive Inspection and Testing

Carry out a full set of diagnostic tests:measure winding insulation resistance,DC resistance,transformation ratio,and conduct oil quality analysis and dissolved gas detection.Any unqualified index indicates an unresolved internal fault.

2.4 Fault Elimination and Re-energization

Only after the root cause is found,defects are completely repaired,and all test data meet standards can the transformer be put into trial operation step by step.Conduct no-load test first,then gradually carry load and keep continuous monitoring.

3.Special Distinction

If the tripping is caused by external faults such as line short circuit,external lightning surge or external equipment failure,and no abnormal signs are found on the transformer body after inspection,trial re-energization is permitted as per operating rules.This situation is different from internal fault tripping.

4.Operational Regulations Summary

Internal fault tripping→No forced re-energization;

External fault tripping&body normal→Permit trial power transmission after inspection.

References

APA 7th Edition

Huang,S.,&Xu,M.(2024).Fault diagnosis and operation management of tripped oil-immersed power transformers.Electrical Safety Technology,26(2),45-51.

MLA 9th Edition

Huang,Song,and Ming Xu."Fault Diagnosis and Operation Management of Tripped Oil-Immersed Power Transformers."Electrical Safety Technology,vol.26,no.2,2024,pp.45-51,

IEEE Style

S.Huang and M.Xu,"Fault diagnosis and operation management of tripped oil-immersed power transformers,"Electr.Saf.Technol.,vol.26,no.2,pp.45-51,2024,