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In order to apply the frequency domain spectroscopy test technology to nondestructively test of ageing state for large electric machine stator bar insulation, we conducted accelerated ageing tests on the epoxy-mica insulation of stator bar under the combined action of multiple factors such as heat, electricity, and machinery, and tested the frequency domain spectroscopy of samples with different ageing degrees. The Davidson-Cole model parameters of frequency domain dielectric response were extracted as characteristic parameters by least square method, and the ageing degree of epoxy-mica insulation was analyzed according to the parameters. Finally, the relationship between characteristic parameters and ageing time was established by fitting. The results show that the dielectric loss factor (tanδ) of epoxy-mica insulation increases with the increase of ageing degree, especially at the frequency of 10-3–10-1 Hz; the characteristic parameters β and τ extracted by the Davidson-Cole model can be used to characterize the ageing degree of insulation. With the increase of ageing time, β decreases linearly, τ decreases exponentially, while Δε increases obviously. A formula for quantitatively characterizing the degree of insulation ageing is obtained through the fitting relationship between τ and ageing time, which can be considered as an empirical formula for evaluating the ageing degree.
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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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