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| The development mechanism of sudden internal faults in large power transformer winding and design improvement measures |
| ZHAO Zhigang |
| China Electric Power Research Institute, Beijing 100192 |
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Abstract In order to prevent sudden insulation faults in the operation of large power transformers, the mechanical damage mechanism of turn insulation during the winding process and the development mechanism of internal discharge in materials such as insulation boards and stays induced by insulation paper damage are analyzed in this paper. Based on the statistical data, the evaluation indicates that under the same conditions, the increased friction force during the winding of high-voltage coils for 220~750 kV transformer is approximately 3.27~17.26 times that of high-voltage coils for 110 kV transformer. On this basis, the possible causes of internal discharge of the insulating material like stays and insulation boards induced by the abnormal insulation of the coil turn are proposed. Furthermore, the internal discharge development mechanism of insulating materials such as stays and insulation boards is analyzed, revealing a discharge development law of “external induction and internal propagation” in these materials. The causes are discussed whereby the development of internal discharge in insulation materials cannot be monitored by online oil chromatography but may lead to sudden and severe insulation failures inside high-voltage coils. Finally, an improved method for the stays in the first oil gap on the inner side of high-voltage coils of large power transformers is explored, aiming to reduce the risk of sudden severe failures caused by the formation of long-scale discharge channels inside coils due to coil abnormalities.
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Received: 27 October 2025
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| Cite this article: |
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ZHAO Zhigang. The development mechanism of sudden internal faults in large power transformer winding and design improvement measures[J]. Electrical Engineering, 2026, 27(6): 77-84.
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https://dqjs.cesmedia.cn/EN/Y2026/V27/I6/77
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2026, Vol. 27 
