Abstract: The research on the influence factors and recognition of electrical fast transient burst (EFT/B) is of great significance to the accuracy of relay protection action in power system. For the phenomenon of malfunction caused by EFT/B in the transformer neutral point gap protection, this paper studies its impact on the transformer neutral point overvoltage. Based on the existing segmented arc model, a simplified model is proposed to reduce the difficulty of establishing the traditional simulation model. On the basis of the analysis of the field relationship of breaker, a new method is proposed to determine the alternating current (AC) arc. In order to study the circuit breaker breaking at different times, breaking of different short-circuit types, breaking at different speeds on the impact transformer neutral point over-voltage size, this paper establishes a circuit breaker model in MATLAB. The time-frequency characteristics and energy distribution characteristics of different transformer neutral point overvoltages caused by EFT/B, lightning and single-phase grounding respectively are generated by using wavelet decomposition. Further, a criterion is set up according to the high and low frequency energy ratio. The simulation results show that the criterion can distinguish the three kinds of overvoltages accurately.