Effect of Thickness on the Breakdown Characteristics of Organic Insulation Materials under Microsecond Pulse Voltage

Thickness affects the electrical breakdown strength (EBD) of insulation materials, and the variation of EBD with thickness (d) is an important basis for insulation design. In this paper, the effect of d on three kinds of organic insulation materials (OIMs), namely polymethyl methacrylate (PMMA), polyetheretherketone (PEEK), and polyethylene terephthalate (PET), on their breakdown characteristics under microsecond pulse voltage (MSPV) was studied, and a breakdown probability prediction model was established based on Weibull distribution. The breakdown mechanisms of the OIMs under MSPV were also discussed. The results showed that the EBD of all three materials decreased with increasing d. The relationship between characteristic EBD and d all satisfied the inverse power model, and their inverse power coefficients were all close to 1/2.3, which was much larger than 1/8 for that under nanosecond pulse voltage. A general breakdown probability prediction model of the OIMs was established by combining the Weibull distribution and beta = 2.3 so as to guide engineering design in the absence of basic test data under MSPV. The breakdown mechanism of the OIMs under MSPV was an energy-related composite physical breakdown mechanism, which was verified by analysis of energy accumulation characteristics and experimental evidence of the little influence of pulse width on EBD under MSPV. The research results lay the foundation for the insulation design and further study on the breakdown modeling of OIM under MSPV.