Experimental Study of Plasma Breakdown in Zero-Air - SF₆ Mixtures for High Voltage Switch Applications

A common dielectric gas used for high voltage switch operation is sulfur hexafluoride (SF6). While having desirable performance, SF6 is cost prohibitive and presents significant supply chain challenges. Thus, it is desirable for SF6 to be removed from current systems. This contribution presents experimental data for the operation of a high voltage switch system using stainless steel electrodes spaced 3.5 mm apart. The system is pressurized in ranges from 80-180 kPa with various mixtures of zero air and SF6. The system load is tuned with an aqueous liquid resistor filled with a sodium chloride and deionized water solution. Resistive measurements are used to generate various Paschen curves (breakdown voltages) for these gas mixtures. The linearity of these created curves is examined. Additional long data series measurements are performed to examine the system performance over many shots with each gas mixture. The data time series are examined by Weibull analysis. The experimental results can be used to quantitatively support possible gas changes within the switches.