The role of HVDC voltage waveforms on partial discharge activity in paper/oil insulation

This paper discusses the role of high voltage direct current (HVDC) voltage waveforms on partial discharge (PD) activity in paper/oil insulation systems. A variety of voltages were simulated by the PSIM software and synthesized using a high voltage amplifier. Kraft paper sheets were used to create defects incepting PD. The PD signals were coupled by a high frequency ferrite core current transformer. PD quantities including PD inception voltage (PDIV), pattern, amplitude distribution and repetition rate were recorded. The results show that the PDIV under notched voltage becomes higher increasing firing and overlap angles. PD patterns change with the HVDC voltage waveforms showing that large PD likely occurs at the rising front of the notches. PD amplitude and repetition rate are both directly proportional to notch depth. It is expected that such results can improve the design of UHV converter transformers.