Dielectric Breakdown Characteristics of Epoxy Resin Induced by High Frequency Electric Stress Used in Solid State Transformer

This paper is dedicated to illustrate the frequency dependence of breakdown strength of epoxy resin insulation used in solid state transformer. The experimental protocol was developed to measure the breakdown voltage of epoxy resin film, including the high frequency power supply (up to 20 kV), measurement and detection units. The frequency of the output high voltage can be reached to 10 kHz. Weibull distribution statistics analysis was employed to discuss the influence of frequency on breakdown characteristics of epoxy resin. The dielectric breakdown strength indicates a reduction with the increase in the frequency of the electric stress. Moreover, the data dispersion of breakdown strength presents slight increase at high frequency. High frequency voltage with harmonics of electric stress caused the reduction of breakdown strength of epoxy resin. It is accepted that partial discharge and increase of dielectric loss led to the reduction of breakdown. Furthermore, the space charge, trapping and polarization should be considered underlying the breakdown mechanism.