Discrimination of Inrush Current Based on Dynamic Magnetizing Inductance Solved by Sinusoid Approximation of Instantaneous Signal

For a long time, the discrimination of the inrush current for power transformer is a perplexing problem. In this paper, a new method used to distinguish the inrush current from the inner fault is proposed. Based on sinusoid approximation of instantaneous signal (SAIS), the dynamic magnetizing inductance in the power transformer can be calculated, whose validity is illuminated with two emulating models. With the character of calculated dynamic magnetizing inductance, distinguishing the inrush current from the short circuit between turns can be processed.