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

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 (μDA), 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 μDA, 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.