Polarity effect of streamer discharge in propylene carbonate under microsecond regime

Propylene carbonate (PC), due to its high permittivity and large resistivity, has a great potential to be used as an energy storage medium in the compact pulsed power sources. In this paper, both the positive and negative breakdown characteristics of PC are investigated and the streamer patterns are obtained by ultra-high-speed cameras. The experimental results show that the positive breakdown voltage of PC is about one time higher than the negative one, which is abnormal compared with the common liquid. The shape of the positive streamer is filamentary and branchy, while the negative streamer is tree-like and less branched. Based on these experimental results, a charge layer structure model at the interface between the metal electrode and liquid is presented. It is suggested that the abnormal polarity effect basically arises from the electric field strength difference in the interface between both electrodes and PC. Furthermore, the recombination radiation and photo-ionization also play an important role in the whole discharge process.