Characteristic of Surface Streamer Discharge Under the AC–DC Composite Voltage

The external insulation of the equipment in the valve hall of ultra high voltage (UHV) dc converter station must be able to withstand ac-dc combined voltage influences. Investigating the surface discharge characteristics of external insulation under ac-dc combined voltage is currently a significant research topic. The investigation into the surface streamer characteristics under ac-dc combined voltage is instrumental in elucidating the mechanism of surface flashover. The streamer characteristics of different phases in a single cycle under ac-dc combined voltage were determined by conducting surface streamer discharge tests. The relationship between surface streamer characteristics and different phases under ac-dc combined voltage was summarized. By comparing the test results of surface streamer discharge under dc voltage, this study analyzed the effect mechanism of ac-dc combined voltage on surface streamer characteristics. The directional motion of space charge under ac-dc combined voltage was identified as the primary determinant of surface streamer characteristics.