Causes of Voltage Transformer Failure

by Starlight Generator dieselgeneratortech

What causes voltage transformer failure in diesel generator?

1.Winding turn to turn short circuit

Fault phenomenon: During operation, the temperature rises, there is discharge sound, the high-voltage fuse is blown, the secondary side voltmeter indication is unstable.

Reason: System over-voltage, long-term overload operation, aging insulation, poor manufacturing process.

2.Insulation damage between iron chips

Fault phenomenon: temperature rise during operation.

Reason: Poor insulation between iron chips; Poor service environment; Long term operation at high temperature promotes aging of insulation between iron chips.

3.Poor contact between grounding lug and iron core of diesel engine

Fault phenomenon: There is discharge sound between iron core and oil tank during operation.

Reason: The grounding plate is not inserted tightly, and the mounting screw is not tightened.

4.Core loosening

Fault phenomenon: There is abnormal vibration or noise during operation.

Reason: The iron core clamp is not clamped, and the iron chip is loose.

5.Winding break.

Fault phenomenon: During operation, there may be arc and discharge noise at the disconnection. The voltmeter indication of the broken phase is reduced or zero.

Reason:The winding leads are broken due to poor welding process, insufficient mechanical strength or unqualified outgoing wires.

6.Winding to ground insulation breakdown

Fault phenomenon: The fuse on the high voltage side of the diesel engine is continuously blown, which may cause discharge noise.

Reason: The winding insulation is aging or there are conductive sundries in the winding, the insulating oil is damped, over-voltage breakdown, serious oil shortage, etc.

7.Short circuit between winding

Fault phenomenon: the fuse on the high-voltage side is blown, the oil temperature is increased sharply, and even the fuel injection is smoking.

Reason: the winding insulation is aging, the insulating oil is damped, and there is serious oil shortage.

8.Discharge flashover between casings

Fault phenomenon: fuse on high voltage side is fused and bushing flashover is discharged.

Reason: mechanical damage of casing due to external force. There are foreign matters or small animals entering between casings, the casings are seriously polluted and the insulation is poor.

When using voltage transformer, what should we pay attention to?

1.We should operate with a suitable transformation ratio, rated capacity, accuracy level. And consider that the voltage drop caused by the secondary wiring will affect the measurement results, so the length can not be too long.

2.The primary winding of the voltage transformer is connected to the line, and the secondary winding is connected to the measuring instrument and relay. When wiring, pay attention to polarity group and phase, and do not connect them wrong.

3.The primary and secondary sides of the voltage transformer shall be equipped with fuses to prevent short circuit accidents. When working on the secondary circuit, pay attention not to short circuit the secondary side of the voltage transformer, otherwise it will cause overheating and burn the transformer.

4.One end of secondary side of voltage transformer shall be grounded for the same reason as current transformer.

When voltage transformer of generator set failure occurs, we must find out the reasons and remove the problem.