Electric breakdown of SF6 at high pressures up to the liquid state

The impulse and 60 cycle breakdown voltages of SF6 for small spherical electrodes for both the gas and liquid phases are reported. The probable breakdown mechanisms and criteria for estimating the limiting values of breakdown fields are discussed. The results of our impulse breakdown tests for the pressure range of 9 to 380 psia on 3/4 inch diameter spherical electrodes for gaps from 0.04 to 1.2 inches are shown in Figure 1. The gap was irradiated for the gas phase, but not for the liquid phase. It is interesting to note that no discontinuity was found in the impulse breakdown voltage in passing from the gas to the liquid phase, a circumstantial evidence that the breakdown mechanism is similar in the two phases.