The Role of Recoverable and Irrecoverable Defects in DC Electrical Aging of Highly Disordered Insulating Materials,
Abstract
Estimating the likelihood of electrostatic discharge (ESD) in highly discorded insulating materials (HDIM) during application lifetimes is critical in applications including spacecraft and high voltage dc power transmission. The focus of this work is a defect driven model of dielectric breakdown based on a dual-defect assumption. Traditional mean-field theory of breakdown effectively considers the average defect energy and density as the only defect mechanism. The dual-defect model considers high-energy (deep) chemical defects and low-energy (shallow) physical defects. Low-energy defects may have significant thermal recovery rate. Such recoverable defects provide a conceptual physical model for dc partial discharge (DCPD) transient non-shorting events. Dielectric breakdown tests on four common polymers, LDPE, PI, BOPP, and PEEK have been studied in the context of the proposed and existing models of breakdown, together with evaluation using standard empirical Weibull distributions. The resulting fits for voltage step-up to breakdown tests provide reasonable estimations of defect parameters. Static voltage endurance time data show excellent agreement with the dual-defect model. Quantile-quantile analysis demonstrates a strong correlation between DCPD and critical dielectric breakdown. During a typical breakdown test many DCPD are observed prior to the destructive breakdown. The relationship between DCPD and breakdown suggest the possibility for highly accelerated dielectric strength testing of candidate HDIM.