Experimental investigation of the dielectric strength of hot SF6

In SF₆ insulated high voltage circuit breakers the dielectric recovery is a crucial phase during the current interruption process. Due to the complexity of the conditions after current zero, there is still little understanding of the relevant processes determining the dielectric strength of hot SF₆ under these conditions. An experimental setup was constructed in order to investigate the dielectric strength of SF₆ at elevated temperature. The experimental setup consisted of a high current circuit producing a switching arc and accordingly a hot gas cloud as well as a high voltage circuit for testing the breakdown voltage of a plug-plane arrangement (weakly non-uniform field). The breakdown voltage was determined for various temperatures between 300...1700 K at a gas pressure of 0.1 MPa. The obtained breakdown voltages were compared to theoretical estimations. Measurement and prediction show similar trends but the absolute precision was low.