Failure Analysis Of Oil-immersed Transformer

Common faults in transformers during operation include faults in windings, bushings, tap-changers, iron cores, fuel tanks and other accessories.
Winding failure:
The main problems include inter-turn short circuit, winding grounding, phase-to-phase short circuit, broken wires and open welding of joints, etc.
Casing failure:
Scale buildup on the transformer casing causes pollution flashover during heavy fog or light rain, causing single-phase grounding or phase-to-phase short circuit on the high-voltage side of the transformer.
Severe leakage:
If the transformer is leaking oil seriously during operation or continuously leaking from the damaged area so that the oil level can no longer be seen on the oil level gauge, the transformer should be immediately deactivated for leak repair and refueling. The reasons for oil leakage from the transformer include cracked or sealed welds. Parts failed, and the fuel tank was severely corroded and damaged due to vibration and external impact during operation.
Tap changer:
Common faults include poor contact or inaccurate position of the tap changer, melting and burns on the contact surface, and discharge of interphase contacts or discharge of each tap.
Overvoltage:
When a running transformer is struck by lightning, the lightning potential is very high, which will cause an external overvoltage of the transformer. When certain parameters of the power system change, an internal overvoltage of the transformer will be caused due to electromagnetic oscillation. These two Transformer damage caused by overvoltage is mostly caused by breakdown of the main insulation of the winding, causing transformer failure.
Iron core:
The failure of the iron core is mostly caused by the insulation damage of the core screw of the iron core column or the clamping screw of the iron core.
Oil leakage:
If the oil level of the transformer oil is too low, the bushing leads and tap-changer will be exposed to the air, and the insulation level will be greatly reduced, so it is easy to cause breakdown discharge.