An in-depth investigation into the effect of oil pressure on the complete statistical performance of a high pressure, flowing oil switch

Abstract

A high pressure, flowing oil dielectric switch was developed for high performance, high voltage switching, and extensively 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 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 – 10 MPa (72 – 1450 psig), oil flow rates from 10 – 40 Lpm (2.6 – 10.6 gpm), peak modulator charge voltages from 12.5 – 25.0 kV, and gap separations from 0.40 – 1.00 mm, utilizing self-breakdown at repetition frequency of 2 Hz. In this paper, we review the effects of operating the switch over the full range of oil pressures at constant modulator charge voltage, constant gap separation, and constant oil flow rate in a study of the complete statistical performance of the high pressure oil switch. The breakdown characteristics of the high pressure oil switch demonstrate remarkable properties, including a linear dependence relating the oil pressure to both the mean and maximum breakdown electric field strength, independence of the minimum break-down electric field strength on oil pressure, and a decidedly non-linear relationship between oil pressure and breakdown electric field strength standard deviation.