Studies on the dielectric strength of transformer oil under oscillatory impulse voltages

In this paper, the results of investigations carried out on the breakdown characteristics of transformer oil subjected to oscillatory impulse voltage (unidirectional and bidirectional) stresses in the frequency range of 10-100 kHz using needle-plane electrode configuration are presented. For the purpose of comparison, experimental results obtained under AC, lightning and switching impulse voltages are also provided. The effect of gap spacing, frequency, field non-uniformity and polarity on the breakdown characteristics are discussed.