Study On Fault Identification Algorithm For Wide-Area Backup Protection Based On PMUS

Due to the growing of the power grid structure and scale, traditional backup protection based only on local information faces many problems, such as the complication of setting, the more time of action. Besides, it is difficult to give consideration to both sensitivity and reliability. When the power flow transfers, the backup protection is likely to trigger a chain tripping accidents. In recent years, with the widely application of phasor measurement unit (PMU), the voltage and current vector of buses with PMUs can be measured accurately and in real time, which can completely meets the wide-area backup protection for data transimission requirements. Hence, the introduction of measurements from PMU to wide-area backup protection area gets common concern. But given the economy, PMU configuration on all buses is not realistic, so the study on the algorithm of wide-area backup proctection based on limited PMUs has a vital theoretic significance.The fundamental principles of wide-area backup protection system are described firstly, including the structure of wide-area backup protection system, the division of protected area and the searching of fault zones.A fault identification algorithm for wide-area backup protection combined with voltage estimation and calculating fault location is studied in this paper. It utilizes one-bus-spaced-placement strategy to distribute PMUs. Taking the node without PMU as center, around wich nodes are configured with PMUs. This algorithm uses the value of the latter voltage and current to estimate the former positive, negative and zero sequence voltage, then calculate the variance for magnitude of positive, negative and zero sequence estimation voltage. According to that when a fault occurred in the line, the estimated magnitude of positive voltage is smaller than the measured value, and the estimated magnitude of negative and the zero voltage is greater than the measured value, sequence criterion can be established. Select the maximal variance, base on corresponding sequence criterion to select the fault line and send a trip signal. Secondly, combined with calculating fault location, distinguish the single line fault and adjacent line with complex fault further, if the latter, the algorithm can identify the other fault line. Simulation results in different fault situation verify the effectiveness of the algorithm.A fault identification algorithm for wide-area backup protection based on limited PMUs is studied in this paper. Firstly, devide the power grid into some zones, of which boundary nodes are configured PMUs. When fault occurres, the zone which magnitude of sum of positive, negative or zero sequence currents is greater than the threshold is identified as the fault zone. Then in this area, by the pure system fault model and fault components node voltage equations, the fault location of each line can be calculated and the result between 0 and 1 is the fault line. Simulation results in different fault situation verify the effectiveness of the algorithm.