Experimental and Theoretical Study of Corona Inception Threshold in Rod to Plane Electrodes Under AC/DC Combined Voltage: Phase Corresponding to AC Voltage

Under AC/DC combined voltage, the corona inception phase corresponding to AC voltage is not a fixed value and will change within a certain range. In this article, the effects of DC polarity, DC proportion, rod radius, and rod-plane distance on corona inception phase were explored. The results showed that the normalized amplitude under equivalent positive corona conformed to normal distribution. In addition, with the increase of DC proportion, the distribution of corona inception phase under equivalent positive corona was more dispersed, and the dispersion changed more obviously than that under equivalent negative corona. When the DC proportion was increased from 25% to 75%, the interval width of phase under equivalent positive corona and equivalent negative corona increased by at most 50° and 15°, respectively. A fluid model was built to explain the change of phase dispersion from the perspective of space charge. The existence of corona inception phase resulted in the difference between AC instantaneous voltage and AC peak voltage at corona inception time, which was of great significance to the study of corona inception.