Effect of gas type on high repetition rate performance of a triggered, corona stabilised switch

This paper reports on the work undertaken to determine the effect of the gas type on the high repetition rate performance of a triggered corona stabilised (TCS) closing switch at a charging voltage of 23 kV. The voltage/pressure (V/p) characteristics as well as the ability of the switch to operate at high repetition rates were measured with SF₆, air and six different SF₆/air mixtures having an SF₆ concentration ranging from 75 to 2% by pressure. The high repetition rate tests were conducted with a high-power facility at a pulse repetition frequency (PRF) ranging from 500 Hz up to a maximum of 3 kHz. During the investigation, it was found that for the given nonuniform switch geometry the high repetition rate performance of the device was closely associated with the efficiency of corona stabilisation, as measured from the V/p characteristics. This was clearly manifested by the superior performance of most of the SF₆/air mixtures tested, which displayed a more efficient corona stabilisation compared to pure SF₆. In contrast, air displayed the worst performance of all the gases tested, due to the weak V/p characteristic and inefficient corona stabilisation.