The effect of conductivity on streamer initiation and propagation between dielectric-coated sphere-plate electrodes in water

A dielectric-coated sphere-plane electrode system was designed and used for the generation of streamer discharges in water. To study the streamer initiation and propagation mechanisms, the effect of conductivity was investigated under pulse voltage. Increasing water conductivity caused the decrease of streamer initiation voltage and streamer formation time delay. Under the same applied voltage, the maximum streamer length was inversely proportional to water conductivity, whereas the streamer brightness was proportional to the water conductivity. The mean streamer velocities were dramatically different with different water conductivity and the influences of interactions between streamer branches on the streamer propagation were inevitable under high applied voltage. Based on the analyses of these experimental results, it can be concluded that streamer initiation in water is triggered by the microgap breakdown in the coating while streamer propagation may be a gaseous or electronic process, which is dependent on applied voltage and water conductivity.