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The thermal effect in the long-term operation of pumped storage generator sets will cause adverse effect on the main insulation performance of stator bars. Taking the VPI stator bar of an 18 kV pumped storage generator as the research object, we prepared samples and designed thermal ageing scheme. By means of dielectric property test, conductivity test, and breakdown characteristic test, the electrical properties of stator insulation under different ageing temperatures and different ageing cycles were explored. The test results show that there is obvious and complete loss peak in the bending section of stator bar. During the thermal ageing process, the dielectric constant frequency spectrum of insulating material shows an increasing trend with the increase of ageing period, and the dielectric constant of the bending section shows a stepwise decreasing trend with the increase of frequency. As thermal ageing progresses, the conductivity of samples increases gradually, and the absorption ratio and polarization index both show a decreasing trend. The breakdown strength of the straight section sample and the bending section sample continues to decrease, and the breakdown strength of the bending section sample decreases more significantly.
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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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