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Analysis of Vibration Signal Caused by DC Bias at Different Measuring Points of Transformer

Power transformer is easy to be invaded by the stray current of urban rail transit, resulting in DC bias. Then the DC bias will lead to severe vibration of the transformer. By analyzing the characteristics of the surface vibration signal of the transformer, whether the transformer is invaded by the stray current can be judged. In this paper, the time domain and frequency spectrum information of vibration signals of six measuring points of 220kV transformer are summarized and compared. Finally, it is concluded that for the 220kV transformer, among the 6 selected measuring points, when the neutral current changes, the vibration signal of the center point of transformer box surface of intermediate phase changes most obviously. Hence, for 220kV transformer, the center point of transformer box surface of intermediate phase is the most suitable for measuring vibration signals caused by DC bias.