Analysis Of Distance Protection For Asymmetrical Transmission Line

Transmission lines include transposed transmission lines,un-transposedtransmission lines and incomplete transposed transmission lines. Because oftwo-phase transmission in the railway system, transmission lines are of their distinctcharacteristics of asymmetrical parameters. Because the length and the load of everytransmission line are unequal, transmission lines are asymmetrical in powerdistribution networks. It is a very important research project in the power system thathow to solve the problem of asymmetric transmission lines. It is very valuable tosteady operation and fault diagnosis of the power system that to solve the problem.Against asymmetry transmission lines which are of their distinct characteristicsof asymmetrical parameters , the method was proposed which could be used toanalysis asymmetric transmission lines by the method of symmetrical components bythe means of researching fault analysis and setting of relay protection of transposedtransmission lines. The influence of characteristics of transmission lines parameterson the distance protection was analyzed by the method of symmetrical components.The influence of characteristics of transmission lines parameters on the distanceprotection was analyzed by the method of symmetrical components. The method ofsymmetrical components was proved to be very effective by detailed analysis andcalculations for symmetrical/asymmetrical transmission line. The analysis resultshowed that the new impedance which was proportional to the fault distance had to dowith the ratio of phase voltage to phase current when a single line-to-ground faultoccurs, other new impedance which was proportional to the fault distance had to dowith the ratio of phase-to-phase voltage to phase-to-phase current whenphase-to-phase ground fault occurs, another new impedance which was proportionalto the fault distance had to do with the ratio of phase-to-phase voltage tophase-to-phase current when phase-to-phase fault occurs.By the above analysis, the new distance protection algorithm basing the methodof symmetrical components is proposed. The new algorithm is extended to solve theproblem of a single line-to-ground fault, phase-to-phase fault and phase-to-phaseground fault in asymmetrical transposition transmission lines. The results of PSCADhave confirmed the reliability and validity of the new algorithm. The algorithm which is used to solve faults in asymmetrical transposition transmission line is of profoundtheoretical value and practical significance.