The performance of polypropylene film determines the reliability of capacitors. This paper studies the change of insulation characteristics of the insulation dielectric polypropylene of high-voltage capacitors during the long-term operation process. Moreover

the correction of the insulation failure model of polypropylene media is implemented. Some conclusions are drawn from a series of experiments. The breakdown strength of the insulation dielectrics decreases as the withstand time rises

with a maximum decrease of 37.91% compared to the polypropylene sample without withstand voltage. As the electric field increases from −20 to −100 kV/mm

the total amount of space charge

the trap energy level and the trap density inside the polypropylene increase by 524.15%

18.99% and 773.36%

respectively. In the capacitor simulation model

the electric field in the capacitor increases by 19.62% after presetting space charge relative to the nonspace charge. The experimental data are substituted into the inverse power model

and the trap parameters are used to modify the model. The results show that the ageing state of the polypropylene has a negative exponential relationship with the trap parameters. This paper provides an important reference for the study of the failure mechanism of polypropylene in high-voltage capacitors and the assessment of polypropylene ageing state.