Research and Determination of Aging Life for New Environmentally Friend ly Polypropylene Insulation Materials

As an emerging insulation material for medium voltage power cables, aging life determination of environmentally friend ly thermoplastic polypropylene needs to be urgently carried out.Focusing on tw otypes of polypropylene insulation materials for medium voltage AC cables, oxidation induction period variation characteristics of polypropylene under high thermal stress conditions were investigated.Linear fitting was used to calculate the parameters in Arrhenius equation, and life-temperature curve of polypropylene was derived.Besides, electrical aging characteristics of polypropylene were studied in constant voltage, stepwise, and stepwise boosting tests.Linear regression and least squares estimation were used to obtain electrical aging life index and life model in inverse power law (IPM model).Results showed: ①Range of electrical aging life index (n) for two types of polypropylene insulation materials was 12.65~16.68 and 12.84~14.68, respectively, and both materials could operate effectively for more than 40 years when temperature was below 90 ℃ and field strength was at and below 19 kV·mm^-1; ②Life model of polypropylene solved by stepwise boosting accumulation method and least squares estimation method was more accurate; ③There was a certain correlation between electrical aging life of polypropylene insulation materials and their crystallization characteristics.The study could provide theoretical support for promotion and application of new polypropylene medium voltage power cables.