Partial discharges (PDs) of solid insulation and lifetime under high-frequency electric stress with steep pulse pose challenges for the design and reliability of high-power density and high-frequency transformers. In this paper

the insulation surface discharge model was taken as an example

and the ultra-high frequency PD measurement method was used to study the influence of frequency and steep pulse parameter (du/dt) of high-frequency square wave on the surface PDs and lifetime of epoxy resin. A lifetime model for epoxy resin insulation under high-frequency square voltage coupling with frequency and du/dt was also established. The denoised PDs signal was obtained through the utilization of a high-pass filter

in conjunction with complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN) and wavelet denoising techniques. The research results indicate that the amplitude of PDs gradually decreases with the increase in square wave voltage frequency and du/dt increase (1~20 kHz). In addition

the lower the frequency is

the greater the difference in PDs amplitude of epoxy resin under different du/dt will be. It is related to the rate of charge decay

where PDs become more concentrated and the discharge amplitude is smaller under high du/dt condition. The lifetime of epoxy resin insulation significantly decreases with an increase in square wave voltage frequency

and it also decreases with an increase in du/dt. Moreover

the lifetime model with frequency and du/dt coupling is established using orthogonal experiments and coupling factor analysis. A comparison between the model results and experimental data reveals an error of less than 3%

confirming the accuracy of the proposed lifetime model. This investigation presents significant implication in the insulation design and application of high-power high-frequency transformers.