UHF PD-detection in a power transformer

The detection of partial discharge (PD) in high voltage insulation is an effective way to determine dielectric faults in the early stages of development. Partial discharge detection in a power transformer was made possible by use of the acoustic detection technique and also by the UHF detection technique. Floating metal parts and partial discharges were detected in paper insulation in a 110/10 kV transformer. The discharge patterns and detection sensitivity obtained with several discharge sources in transformer oil were presented. The UHF technique is considered an ideal method for monitoring and for inspection because of the possibility for automatic classification of the type of discharge and because of its low sensitivity to external noise. It was shown that partial discharge in oil is short in duration and more irregular in time than partial discharge in gas. The UHF technique was also found to be more sensitive because of the lower wave attenuation and classification of the type of discharge. 3 refs., 5 figs.