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An accelerated thermal ageing test was designed for the main insulation sample of a generator VPI stator bar, and the ultrasonic velocity, ultrasonic spectrum, and ultrasonic defect waveform of samples were analyzed at various ageing temperatures on the basis of the principle of ultrasonic testing. At the same time, artificial hole defects and impurity defects were introduced into the insulation samples to explore the effect of defect introduction on the ultrasonic waveform of the samples. The results show that as the thermal ageing test progresses, the overall ultrasonic velocity in the main insulation of stator bar shows a decreasing trend. The reason is that during the thermal ageing process of the stator bar main insulation sample, the layering of internal structure can cause refraction, reflection, and dissipation of the sound wave during propagation process, resulting in the propagation speed of the sound wave in the insulation sample decrease. The defects can be detected and accurately located through ultrasonic echoes, which indicates that the acoustic performance testing method has good practicality in the diagnosis of stator bar main 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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