Underwater Positive Streamer Propagation with Different Insulation Modes

Application of the high voltage on the electrode system in water can lead to the induction of the streamer and the propagation of the streamer to the opposite electrode. In this paper, an underwater electrode system with a gap distance of 10mm is constructed. It is convenient for this system to investigate the development of the streamer. Whether the tip of the positive needle electrode is directly exposed to water is called direct liquid discharge or dielectric discharge, respectively. It is shown that during the pre-breakdown process, the positive streamer generated by direct liquid discharge is always induced near the positive needle electrode. The lower leakage current is beneficial to induce the breakdown voltage and improve the propagation speed. When the voltage across the gap is low, the gray bush-like subsonic streamers in the beginning is eventually turned to the bright filamentary supersonic streamers. In addition, the influence of the non-uniformity level of the electric field on the development of the initial streamer is compared and analyzed. Besides, one way to effectively reduce the pre-breakdown leakage energy is put forward.