A novel adaptive scheme of discrimination between internal faults and inrush currents of transformer using mathematical morphology

This paper addresses a new relaying scheme for identifying the inrush current and short circuit current caused by internal fault on the basis of sudden changes detection using novel morphological gradient (NMG), transient current signals are then extracted by use of morphological opening and closing transform. Based on different characteristics of transient signals between the short circuit current and the inrush current, the transformer protection method is proposed. This method can avoid the symmetrical inrush current and saturation of current transformer (CTs). The results of Electrical Power Dynamic Laboratory (EPDL) indicate that the proposed technique can also deal with the sampled data contaminated with various kinds of noises and DC components and is stable during internal faults with external shunt capacitance in a long EHV transmission line