Directional element of distance relay for symmetrical fault during power swing

To ensure the correct directional decision for close-up symmetrical faults, a distance relay normally relies on the conventional memorized polarization based directional element, which calculates the phase angles between a memorized pre-fault voltage and a fault loop current. This paper analyzes the performance of this directional element during power swing, and the results show that it is not reliable for close-up faults and might cause mal-operation of distance relay. This paper further presents the positive sequence super-imposed components based directional element, and studies its performance during power swing. The study results show that this directional element is reliable for symmetrical faults during power swing. EMTDC simulation results have verified the analysis results.