Analysis of partial discharge activity in line-commutated HVDC converter

This paper presents partial discharge (PD) activity in line commutated high voltage direct current (HVDC) converter. Poorly impregnated kraft paper sheet was designed to simulate the field cavity defect and generate PD signals, which were detected by a Rogowski coil sensor in experiments. The dependence of partial discharge inception voltage (PDIV) on the characteristics of the applied waveform, that is, a sinusoidal voltage affected by notches due to commutations was reported. The experiments show that the PDIV under notched voltages becomes larger increasing the firing and overlap angles. Also, the characteristics of PD activity and pattern under the AC notched voltages were carried out. The results show that the PDs occur more intensively in the presence of voltage notches. Thus, it is expected that the lifetime of paper-oil insulation under AC notched voltage could be shorter than that under pure AC sinusoidal voltage.