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When flashover and other accidents occur on the composite insulator in operation, the temperature rises steeply. Combined with the synergistic effect of electric field, the silicone rubber used for composite insulator will crack and destroy rapidly. In this paper, molecular model of silicone rubber was established, and then the mechanism and characteristics of electrothermal cracking of silicone rubber under steep temperature rise were studied based on the reactive force field simulation, in order to compensate for some limitations of macroscopic tests. The results show that in the flashover development stage, temperature and electric field have different mechanisms of action on the cracking of silicone rubber, temperature plays a dominant role, and electric field decreases the cracking temperature and accelerates the deterioration of material. The cracking process is triggered by the breakage of Si-C bonds, with CH4, H2, C2H4, C2H2, and H2O as the main products at different stages. The number of Si-CH3 bonds decreases by about 40% with a large number of methyl groups shed from the main chain of silicone rubber. With the further destruction of the main chain structure and the formation cross-linked structure, the number ratio of Si-O-Si bond to Si-C bond and the carbon hydrogen ratio increase continuously, the maximum is 2.93 times and 1.87 times higher than that of the pre-cracking level, respectively. The diffusion of impurity gas products dominated by H2 generates voids in the material, leads to the structural reorganization, results in the insulation failure eventually.
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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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