Statistical Properties of Corona Current Pulses in Rod-Plane Air Gap Under AC–DC Composite Voltages

In this article, the corona discharge in rod-plane air gap under ac-dc composite voltages was measured by noninductive resistance and MPD 600 partial discharge measurement system. The characteristics of corona discharge pulses under ac-dc composite voltages were interpreted by phase resolved partial discharge (PRPD) patterns. The corona discharge inception voltage (CDIV) of rod-plane air gap under ac-dc composite voltages was measured and predicted theoretically. The charge of positive corona discharge (PCD) is much larger than that of negative corona discharge (NCD), and the repetition rate of PCD is much smaller than that of NCD, which is due to the difference in the production mechanism of initial electron. The repetition rate and phase distribution range of discharge pulses decrease with the increase of ac component when the amplitude of ac-dc composite voltage is a constant. The weighted pulse sequence analysis (WPSA) was used to analyze the corona discharge pulses under different applied voltages. The WPSA plots of PCD and NCD have different characteristics, and the WPSA plots under ac-dc composite voltage have greater dispersion than that under dc voltage. This work provides a new perspective for the analysis of corona discharge pulses under ac-dc composite voltages, which will be helpful to the location and identification of equipment defects under ac-dc composite voltages.