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Free metal particles are usually regarded as one of the most hazardous contaminants in the liquid-phase insulation of converter transformers, which can lead to the partial discharge (PD) initial voltage and breakdown voltage of equipment decrease obviously. In this paper, a transformer oil circulation system was constructed, and DC partial discharge and breakdown experiments were conducted on the transformer oil containing metal particles at different oil flow velocity. The PD characteristic parameters were extracted, and the variation of characteristic breakdown voltage with oil flow velocity was obtained. Then the affecting mechanisms of oil flow velocity on the PD and breakdown characteristics were discussed combined with the particle distribution images between electrodes. The results show that when the oil is static, the partial discharge degree of the transformer oil containing metal particles is highest. With the increase of oil flow velocity, the PD initial voltage increases, and the discharge repetition rate and the accumulation discharge magnitude per unit time decrease. When the oil is static, the breakdown voltage of the transformer oil containing metal particles is lowest. With the increase of oil flow velocity, the Weibull distribution curve of breakdown voltage shifts to the right, and the characteristic breakdown voltage increases, that is, the flowing of oil improves the insulating properties of transformer oil and reduces the breakdown possibility remarkably.
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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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