Modeling Dielectric Breakdown of Voids in Ground-Wall Insulation Systems: Initial Studies

The ability to anticipate voltage-induced breakdown (BD) of electrical insulation is of critical importance to the power industry to maintain uninterrupted electrical service and ensure grid reliability. Gaseous voids trapped within the electrical insulation of power devices are an often unavoidable artifact of the manufacturing process. The compromising effect of voids on dielectric performance of motors and generators is difficult to predict as these effects are dependent on highly localized field geometries. Reported here are initial steps toward the development of a FEA simulation model which will help inform machine insulation design by predicting breakdown thresholds under device-specific configurations and conditions. Preliminary results consider a simplified test system of two opposing electrodes sandwiching an air gap. A finite element simulation was developed using COMSOL Multiphysics utilizing a newly released software add-on, the COMSOL Electric Discharge Module, to model the electric field generated within this simplified system under an applied DC terminal load. Electric field characteristics and associated gas breakdown thresholds were determined as a function of several geometric and environmental parameters. Modeled system geometry was specifically designed for rapid evaluation and experimental validation in the lab. Experimental air breakdown data was generated and found to be in agreement with simulated data.