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Power electronic transformer (PET) insulation system continue to deteriorate in high frequency, high voltage, short rise time pulse electrical stress and high temperature and other harsh environments; insulation discharge and breakdown risks are increasing significantly. In order to study the effect of high temperature thermal aging for PET on insulation deterioration under real operating conditions, the typical insulation polyimide (PI) of PET was aged at 250 ℃ for 3, 6, 9, 12 days, and then 20 kHz, 4 kV, 300 ns pulsed voltage was used to simulate PET operating conditions. The partial discharge and breakdown voltage of insulation were tested, and time-resolved partial discharge spectrum (TRPD), discharge times, average discharge amplitude, and maximum discharge amplitude were used to characterize the degree of insulation deterioration. The results show that after aging, the TRPD pattern of PI films changes from single peak to multiple peaks, showing a phenomenon of clustering. At the same time, with the increase of aging time, the number of partial discharges, average discharge amplitude and maximum discharge amplitude increase by 47.3%, 61.1% and 41.9%, respectively, and the degree of insulation deterioration was significantly deepened. The breakdown voltage distribution of PI film conforms to Weibull distribution and decreases with aging time, from the initial 4 667 V to 4 457 V, a decrease of 4.5%. Therefore, the effect of aging time on the deterioration of PET insulation is obtained, which has certain guiding significance for the reliability analysis and optimal design of PET insulation.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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