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Bushing is an important component of oil-immersed transformers, and its internal insulation moisture, ageing, and development of some defects after long-term operation will cause distortion of local electric field, which seriously threatens the safe operation of bushing. In this paper, the variation patterns of dielectric parameters of the aged and damped oil-immersed paper under different test temperature environment were obtained, and a dynamic dielectric parameter calculation model was established. Meanwhile, a simulation model was established on the basis of actual structure of a 252 kV/1 250 A bushing. Electro-magnetic-thermal coupling multiphysics were used to conduct simulation analysis, and the transient electric field distribution and distortion severity inside the bushing under three typical defect conditions were obtained. The results indicate that when the end screen of bushing is unreliable grounding (resulting in floating potential), electric field distortion occurs at the contact side of bushing and end screen, and the voltage grading effectiveness of capacitive core is weakened. When there is wrinkle on the capacitance screen of bushing, the maximum electric field intensity at the wrinkle regions increases proportionally with the bending curvature. Notably, the field strength inversion phenomena are observed at the distortion zones when the capacitance screen reach specific bending curvature. The bubbles attached on the end screen surface have greater influence on the electric field distribution than bubbles dispersed in transformer oil. Such surface-attached bubbles are prone to produce partial discharge.
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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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