An In-depth Investigation of the Effect of Oil Pressure on the Complete Statistical Performance of a High-pressure Flowing Oil Switch

A high-pressure flowing oil dielectric switch was developed for high-performance, high-voltage switching. It was evaluated by a team at the University of Missouri-Columbia. The switch was designed to produce a continuous train of nanosecond-rise electrical impulses, with a peak output power ranging up to several gigawatts, and at repetition frequencies ranging up to several kilohertz. High-pressure flowing oil was proposed for the switching medium as a means of enabling the rapid recovery of the insulating properties of the dielectric following electrical breakdown. The switch was developed for self-breakdown operation, with an anticipated lifetime of greater than 10⁷ switching cycles. An experimental study of the statistical performance of the high-pressure flowing oil switch was conducted over a range of oil pressures from 0.5 to10 MPa, oil flow, peak modulator charge voltages from 12.5 to 25.0 kV, gap separations from 0.50 to 1.00 mm, and at an oil flow rate of 20 Lpm. The switch was designed for self-breakdown operation at repetition frequencies of up to 100 Hz, though the experiment was conducted at 2 Hz. The breakdown electric field strength was found to follow a Weibull probability density function. The effect of increased oil pressure was to flatten the distribution with an asymmetric negative skew. The peak charge voltage was found to have virtually no effect on normal breakdown. The gap separation produced the largest effects observed, resulting in an increase in the average breakdown electric field strength with decreased gap separation, and a decrease in variance with increasing gap separation.