High-Frequency Breakdown Characteristics and Insulation Failure Analysis of Epoxy Resin for Power Electronic Transformers

Insulation systems in power electronic transformers are subjected to long-term high-frequency and high-voltage electrical stress, increasing the risk of failure. This study prepared epoxy resin samples for encapsulation insulation in power electronic transformers and tested their high-frequency breakdown characteristics in the 10 kHz to 100 kHz range, analyzing the results using Weibull distribution. Scanning electron microscopy was utilized to investigate the microstructure of the epoxy resin after high-frequency insulation failure. The results showed that the high-frequency breakdown strength conformed to the Weibull distribution, with the scale parameter decreasing and gradually reaching a threshold as frequency increased, ranging from approximately 66 kV/mm to 84 kV/mm. The epoxy resin samples prepared using the scraping method exhibited no significant insulation defects in their morphology. Post-insulation failure, the surface and cross-sectional morphology of the epoxy resin displayed distinct characteristic features.