Discrimination between magnetizing inrush and fault currents in single-phase transformers using power method

This paper presents a numerical power method to discriminate the magnetizing inrush current from the fault currents in single-phase transformers. The proposed technique is based on the average power flowing into transformers during the fault current or the transformer inrush current. The internal fault consumes power larger than what the inrush current consumes. Hubert transform is used to calculate the instantaneous average power during these transients. The average power is calculated by integrating the instantaneous average power within a period of the fundamental frequency. The method is applied to a 1 kVA, 220/110-V, 50 Hz single-phase transformer. The results obtained in this paper show that the method is simple, practicable, and the two transient currents are effectively discriminated.