Study on adaptive relay protection scheme based on phase measurement unit (PMU)

An adaptive setting scheme for distance protection relay based on phasor measurement unit (PMU) is proposed in this paper. Impedance of the transmission line is calculated to implement on-line setting of first zone distance protection. The voltages and currents of the two terminals of the transmission line and the current of the next transmission line from PMU can be used to obtain the synthetical system impedance that is used to obtain branch coefficient to implement online setting of second zone protection. Co-ordinated setting of distance protective relays can be carried out by the proposed method. Extensive EMTP simulation results have indicated that the equivalent operation mode of power system and the branching factor of protection can be obtained, and the on-line setting scheme can further raise the sensitivity of protection as well as insuring the selectivity and reliability of protection.