Electrical Breakdown and Dielectric Recovery of Propylene Carbonate

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