Using mathematical morphology to discriminate between internal fault and inrush current of transformers

This study proposes a novel scheme using mathematical morphology to effectively discriminate between the internal fault and inrush currents of power transformers. The proposed scheme consists of two parts. The first part is based on morphological gradient (MG), for discrimination of currents occurring without considering the current transformer (CT) saturation. The second one uses a symmetrical criterion involving MG to identify internal fault current under CT saturation. To demonstrate its compatibility and efficiency, the scheme is verified employing the data simulated using PSCAD/EMTDC and data collected from laboratory experiment, respectively. The simulation and experimental results indicate that the proposed scheme can improve the accuracy of inrush current identification, even under certain extreme conditions.