New aging diagnostics for microdischarge assessment of high dV/dt stressed mica paper capacitors

Abstract

Very fast dV/dt pulsing influences the amount of subpicocoulomb microdischarges observed in reconstituted mica paper capacitors. These microdischarges are analyzed by means of a new aging diagnostic technique. This new approach involves the measurement of the microdischarge inception voltage-the point when microdischarges reach approximately 0.5 pC-and its dependence on the quantity and magnitude of high dV/dt stressing. Taking into account mica's robust nature in thermal environments, little effect from high dV/dt pulses is observed in the material. However, aging does occur at the electrode-mica interface. The Energy Systems Institute (ESI) has developed, over many years, research oriented diagnostic tools for measuring microdischarges on various materials. The Biddle Micro Discharge Analyzer (/spl mu/DA), developed at the ESI in conjunction with AVO-Biddle, accurately measures subpicocoulomb levels of charge on a sample up to at least 20 kV AC+DC. The Model-9 MIT Hard Tube Pulser (MOD-9) has been updated and improved to voltage stress various samples up to a megavolt per microsecond. The focus of this research combines the abilities of the Biddle /spl mu/DA, with the high dV/dt MOD-9 for looking into the relationship of insulation aging as a function of very fast voltage pulses. As more applications move to pulse power, specifically in the military, there is a critical need to evaluate the ability of certain dielectric materials to survive the transition from traditional DC and/or AC power to high rep-rate pulsed power.