Performance Criterion of Phasor Measurement Units for Distribution System State Estimation

A phasor measurement unit (PMU) is a device that can directly measure the phase angles of voltages and currents, with high accuracy, using accurate time signals. Hence, PMUs have originally been used to improve the accuracy of transmission system state estimation. The merit of PMUs, further, extends the scope of its application to distribution system state estimation (DSSE), which has recently been studied because of the growing needs for distribution system management due to high levels of distributed energy resources. More importantly, the scarcity of measuring sensors in distribution systems highlights the role of PMUs for the DSSE. However, the full deployment of PMUs in distribution systems is practically impossible because of the high installation costs and geographically large size of these systems. Therefore, this paper investigates the adequate and economic performance of PMUs to meet the DSSE requirement with respect to the estimation accuracy. The accuracy of different PMU performance classes and the accuracy of various measurement types are first defined. Different sets of measurements are then assigned to different meter locations in a testbed that is a three-phase unbalanced, asymmetric system. Various performance metrics for each case study are computed and compared from the numerical simulation results.