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 220V transformer are summarized and compared. Finally, it is concluded that for the 220kV transformer, when the peak current of the neutral point changes, the vibration signal of the central point of the box surface of the intermediate phase changes most obviously. Hence, the central point of the box surface of the intermediate phase is the most suitable for measuring vibration signals caused by DC bias.

DC bias,measuring point,transformer,vibration signal