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In order to investigate the effect of continuous changes in high and low temperatures on the epoxy composite insulation of cable terminals, micron Al2O3/epoxy composite insulation samples were prepared in this paper, and thermal-cooling cycling experiments were conducted on the samples. The changes in dielectric properties and degradation mechanism of epoxy composite insulation samples under different number of thermal-cooling cycling were analyzed through the AC breakdown, isothermal surface potential attenuation, and dielectric properties tests. The results show that during the process of thermal-cooling cycling, the cross-linked network of epoxy composite insulation deteriorates gradually under the combined action of high temperature thermal ageing and high and low temperature alternating stresses, the filler gradually separates from the matrix, microcracks and holes appear in the sample, the free volume increases, and the dielectric constant and electric strength continue to decrease. After 750 hours of thermal-cooling cycling, the AC electric strength of the sample decreases by 15.2%, the deep trap density decreases by 41%, the shallow trap density shows a fluctuating trend, and the dielectric loss factor (tanδ) firstly decreases and then slightly increases.
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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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