Abstract: Discrimination between an internal fault and a magnetizing inrush current has long been recognized as a challenging power transformer problem. This paper presents a new method of detection of inrush and fault current considering current waveform and its magnitude and time samples as ADC emulated data. An algorithm is used to compare the data of magnitude and time of both inrush and fault current with the help of FPGA. Decision can be made based on the output of FPGA whether to provide trip circuit for fault current and allow the inrush current to pass through as it exist for a duration lesser than the fault. Several investigations have been carried out on a single phase transformer and simulated for different fault and switching conditions. The results prove that the proposed technique is able to offer fast responses in detection of inrush and fault current.

Keywords: Inrush Current, fault current, FPGA, Differential Relay.