Explain the major causes of transformer failure
The most common cause of transformer failure is insulation failure; it deteriorates due to heat, oxidation, acidity, and moisture. Line surges such as switching surges, voltage spikes, line faults, and also because of distribution abnormalities.
It would also cause because of
Poor earthing system
Low insulation cables
Low or non-availability of oil
Poor winding and improper Termination
Overload and excess voltage
- Winding failure. It mainly includes inter turn short circuit, winding grounding, phase to phase short circuit, wire break and joint open welding, etc.
- Casing failure. The fouling of transformer bushing causes pollution flashover in heavy fog or light rain, resulting in single-phase grounding or phase-to-phase short circuit at the high-voltage side of the transformer.
- Serious leakage. The oil leakage of the transformer during operation is serious or continuously overflows from the damaged place, so that the oil level can not be seen by the oil level gauge. At this time, the transformer shall be stopped immediately for leakage repair and refueling. The causes of oil leakage of the transformer include weld cracking or seal failure, impact by external force during operation, serious corrosion and damage of the oil tank, etc.
- Tap changer fault. Common faults include poor contact or inaccurate position of tap changer, melting and burning of contact surface, discharge of interphase contacts or discharge of each tap.
- Fault caused by overvoltage.
- Failure of iron core. Most of the faults of the iron core are caused by the insulation damage of the through core screw of the iron core column or the clamping screw of the iron core.
- Transformer gas protection fault
- Oil leakage. The oil level of transformer oil is too low, so that the bushing lead and tap changer are exposed to the air, and the insulation level will be greatly reduced, so it is easy to cause breakdown discharge.
- Abnormal sound. During normal operation, the transformer will emit a continuous and uniform “buzzing” sound. If the generated sound is uneven or there are other special sounds, it shall be regarded as abnormal operation of the transformer. The common causes are the loose fixing screws of the transformer, the lack of phase of the power supply at the high voltage side and the overload caused by excessive load.