Fault Analysis Of Oil-Immersed Transformer

Common faults of transformers during operation include faults of windings, bushings, tap changers, iron cores, oil tanks and other accessories.
Winding faults
Mainly include inter-turn short circuit, winding grounding, phase-to-phase short circuit, wire breakage and joint open welding.
Bushing faults
The transformer bushing is fouled, causing flashover in 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
The transformer is leaking oil seriously or continuously overflowing from the damaged part so that the oil level gauge can no longer see the oil level. At this time, the transformer should be immediately shut down for leak repair and refueling. The causes of transformer oil leakage include cracked welds or failure of seals, and the oil tank is severely rusted and damaged due to vibration and external force collision during operation.
Tap changer
Common faults include poor contact or inaccurate position of the tap changer, melting and burning of the contact surface, and discharge of phase contacts or each tap.
Overvoltage
When a transformer in operation is struck by lightning, the high potential of lightning will cause external overvoltage of the transformer. When certain parameters of the power system change, electromagnetic oscillation will cause internal overvoltage of the transformer. The damage to the transformer caused by these two types of overvoltage is mostly caused by the breakdown of the main insulation of the winding, resulting in transformer failure.
Iron core
Most of the causes of iron core failure are caused by insulation damage of the through screw of the iron core column or the clamping screw of the iron core.
Oil leakage
When the oil level of the transformer oil is too low, the bushing lead and the tap changer are exposed to the air, and the insulation level will be greatly reduced, which is easy to cause breakdown discharge.