Application of probabilistic distance measures for inrush and internal fault currents discrimination in power transformer differential protection

Abstract

Differential protection failure in discrimination of inrush and internal fault currents will impose significant challenges and damages both on the power transformers and power systems. To cope with this issue, this paper investigates the application of Probabilistic Distance Measure (PDM) in discrimination of the inrush and internal fault currents in power transformers. The PDMs are essentially employed to determine the dissimilarities between two sets of distributions. This paper utilizes Symmetric PDM, to determine the discrepancy between the differential current signal and the reconstructed differential current waveform. To such aim, at the first step, the reconstructed differential current waveform obtained from CTs is reproduced. The reconstructed current signal contains only sinusoidal parts of the fault current and thus are reproduced using the modified least squares algorithm. Eventually, the reconstructed current and the differential current signals are fed to PDM to determine the distribution discrepancy between the signals. The performance of the proposed PDM criterion is evaluated utilizing experimentally recorded data and is further compared with the state-of-the-art. The obtained results reveal that the proposed index can be successfully applied for the discrimination of inrush and fault currents even in the case of current transformer (CT) saturation.