A sympathetic inrush detection method based on on-line magnet flux calculation

The sympathetic inrush is a hot issue in the field of differential protection research, due to its characteristic of concealment, diversity, and complexity. The mal-operation of differential protection probably caused by sympathetic inrush is still a difficult problem to be solved. This paper proposed a new sympathetic inrush detection method based on the on-line magnet flux calculating by integrating the measuring voltages on the tips of transformer. This method can completely overcome the negative influence of CT saturation on the differential protection from principle. The EMTDC-based simulation results prove the effectiveness of the proposed method and also verify that this method would not decrease the sensitivity of differential protection under the condition of internal fault.