Wide-Area Backup Protection Algorithm Based On Limited PMUS

With the continuous development of the power system, grid structure becomes more and more complex, the configuration and tuning of backup protection based only on local information become more and more difficult. The development of PMU (phasor measurement unit) provides an important foundation for the research of wide-area backup protection, the bus voltage and current vector can be synchronously measured by PMU, but considering efficiency, we cannot distribute PMU at the both ends of any lines, so wide-area backup protection algorithm based on limited PMU configurations is studied in this paper.The structure of the existing wide-area backup protection system is described. The searching and defining method of fault zone, wide-area backup protection algorithm based on electrical quantities are analyzed in detail.A suspected fault line searching algorithm based on least squares estimation method is studied, the algorithm utilizes one-bus-spaced-placement strategy to distribute PMUs. The bus voltage values are estimated by the least squares estimation method and the estimated line current values are calculated using the estimated voltage. Sort the difference of the measured and estimated current values and take the largest two lines as a collection of suspected fault line. Then determine the fault lines by calculating their fault location, judge the fault line which fault location is between0and1. IEEE14bus simulation results show that the algorithm can accurately determine the fault lines without the impact of fault location and fault types.A wide-area backup protection algorithm based on transition resistance is studied, the protection criterion is given by the difference of transition resistance between fault and normal conditions. First, according to the suspected fault line searching algorithm, judge the fault line which current circuit residual is maximum and sends a trip signal, then the transition resistance or impedance value of suspected fault line is calculated based on limited PMUs configuration, protection criterion is given for no branch and two branch cases. IEEE14bus simulation results show that the algorithm can accurately determine the fault lines without the impact of fault location and fault types.