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In order to investigate the performance degradation characteristics of multi-layer Nomex insulating paper used in transformers during the thermal ageing process, firstly, the multi-layer oil-immersed Nomex insulating paper was conducted accelerated thermal ageing test, then a frequency domain dielectric spectroscopy testing platform and a surface potential testing platform were established to obtain the dielectric loss factor and surface potential decay curves of oil-immersed insulating paper at different ageing time, and the surface trap distribution characteristics of the oil-immersed insulating paper with different ageing degree were calculated and analyzed. The results show that with the increase of thermal ageing degree, the dielectric loss factor of oil-immersed Nomex insulating paper samples increases significantly across all frequency bands. The dielectric loss factors of double-layer and triple-layer oil-immersed insulating paper samples are significantly higher than that of single-layer oil-immersed insulating paper sample, and the dielectric loss factor of triple-layer oil-immersed insulating paper sample exhibits an even greater increase. As the thermal ageing degree increases, the initial surface potentials of the insulating paper samples gradually decrease, and the surface potential decay rate increases with ageing time, while at the same ageing cycle, the surface potential decay rate gradually decreases with the increase of insulating paper layer number. The shallow trap density of oil-immersed insulating paper increases with the increase of ageing degree, while the deep trap density decreases. The decline rates of deep trap density and energy level of double-layer oil-immersed insulating paper are lower than those of single-layer oil-immersed insulating paper, while the increase rates of its shallow trap density and energy level are higher than those of single-layer oil-immersed insulating paper. The research results can provide some reference for the design of transformer oil-paper 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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