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Since DC bias is one of the main reasons for increases in the vibration and noise of a large-scale transformer, it is essential to fully understand the vibration and noise characteristics of large-scale transformers under DC bias for the evaluation of the operating state of transformers and the reduction of noise and vibration. A 406 MVA EHV large-scale transformer is taken as the research objective, and its vibration and noise characteristics are studied. First, based on the field-circuit coupling finite element method, the no-load operation characteristics under different DC bias currents are simulated and analyzed, and the law of excitation current under different DC biases is analyzed. Second, a multi-physics coupling model of circuit-magnetic field-solid mechanics-pressure acoustics is established, and the effective value of vibration displacement and the time-frequency characteristics of noise signal at different measuring points of the transformer under DC bias are obtained considering the influence of magnetostriction. Third, the sound level is measured at different measuring points around the transformer, and the simulated value is compared with the actual measured value to verify the effectiveness of the proposed calculation method for transformer vibration and noise. Finally, the Hilbert-Huang transform method is used to extract the vibration and noise characteristic quantities of one large-scale transformer under DC bias, and a transformer vibration characteristic recognition method based on the energy ratio of the noise signal intrinsic mode function is proposed. This method can effectively recognize the severity of DC bias of the transformer and accurately grasp its operating state, providing a theoretical basis for timely taking measures to suppress the DC bias.
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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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