Oscillating impulse voltage waveform has the advantages of high efficiency

suitable for field use andclose to the actual waveform of equipment. It is suitable for field impulse voltage test after equipment handover andoverhaul. In this paper

a 110 k V transformer C-phase winding is tested for oscillating switching impulse voltage.The transformer fault diagnosis is carried out by high and low voltage waveform

neutral current waveform and trans-fer function. It is found that the waveforms of voltage and current have no significant difference before the wave-tailtime. The waveforms of voltage and current changes due to the saturation of magnetizing inductance

which is obvi-ous at high voltage

and the higher the test voltage is

the more obvious the influence of excitation inductance satura-tion is. The peak frequency of voltage transfer function increases at high voltage

while the current transfer functiondoes not change significantly. It shows that the defect is located in the C phase low voltage winding of the transform-er

which is consistent with the conventional test results. The validity of the oscillation switching impulse diagnosistechnology is verified.