Breakdown characteristics of plasma closing switches filled with different gases

When operating gas-filled plasma closing switches, the most commonly used dielectric gas is sulphur hexafluoride (SF6) due to its desirable and advanced dielectric properties. In recent years, concerns over the impact of SF6 on the environment and its contributions to the global greenhouse effect [1], as well as the continual rise in the cost of acquiring SF6 [2] has led to a desire within the pulsed power community to find an alternative switching medium to replace SF6, [3]. The main concern over replacing SF6 is that plasma closing switches filled with any replacement gas must have similar performance parameters to the SF6–filled switches, e.g. parameters such as the DC breakdown voltage and the triggered breakdown voltage, jitter and breakdown voltage spread, the recovery of the switch and the energy losses [4]. This paper presents results obtained for DC breakdown tests in a self-breakdown switch with an adjustable inter-electrode gap that has been filled with argon, nitrogen, atmospheric air and an argon/oxygen mixture at different pressures. As a result of the experimental work conducted, the characteristics of the plasma closing switches filled with different gases have been obtained and compared to previous work carried out [5] as well as compared with the characteristics of commonly used SF6–filled switches. Initial development of the model of a plasma closing switch has been developed which will be developed so that the model can be used for characterising the performance of different pulsed power systems and for optimization of current systems in order to improve their performance parameters e.g. decrease jitter and pre-fire rate, generate tailored wave-forms and improve overall stability of operation