Electrical Breakdown and Dielectric Recovery of Propylene Carbonate

Abstract

Polar liquids are characterized by high permittivity and high dielectric strength. These properties make them appealing dielectrics for use in high-energy storage systems and as high-power switching media. Most of the studies on electrical breakdown and recovery have focused on water as a switch medium in pulsed-power systems. As an alternative to water, the authors have studied the breakdown and dielectric recovery of propylene carbonate (C4H6O 3). One advantage of propylene carbonate over water is its relatively low freezing temperature of -55degC, which allows its use at a high altitude. The permittivity of propylene carbonate is 65, somewhat less than water (81). Its dielectric strength for pulses of 200-ns duration was measured as 2.2 MV/cm, higher than that of water (1.5 MV/cm). A nonlinear increase in conductivity above electric fields of 1.225 MV/cm, assumed to be due to field-enhanced dissociation, was recorded in both cases. The recovery of propylene carbonate is similar to that of water, with plasma decay, shock-wave emission, and vapor bubble formation, except for the very last phase, which is determined by chemical reactions: the generation and decay of polypropylene polymers. This limits the time for dielectric recovery of propylene carbonate switches to values of more than 10 ms