Principle investigation and simulation research on pilot zero sequence directional protection with compensation of negative sequence component

If the zero sequence voltage is not sensitive enough,the pilot zero sequence directional protection will not operate correctly.Considering the negative sequence transfer impedance between stations is much smaller than zero sequence transfer impedance between stations,and the negative sequence voltage is greater than the zero sequence voltage when single phase fault occurs,a new criteria based on the composition of negative sequence component is proposed.The detailed actual applications are considered in the criteria.According to the phase relationship between zero and negative sequence voltage and current after fault,the fault direction can be calculated.After analyzing the characteristic and sensitivity of criteria deeply,the sensitivity can be improved step by step,and then a complete pilot directional earth fault protection scheme is finished.The result of actual system and simulation demonstrate that the criteria can judge the fault direction reliably with good reliability and sensitivity.So the new criteria can effectively improve the performance of pilot directional earth fault protection.