Real Time Voltage-Phasor Measurements for Static State Estimation

Recent introduction of microcomputers in substations to assume all substation tasks including protections makes possible accurate real-time measurements of positive sequence voltage phasors. Since static state estimators use measurements of line flows and injections to estimate the positive sequence voltage phasors it is clear that direct measurement of the state vector may be used to enhance state estimation. In order to obtain simultaneous measurements of different buses it is necessary to synchronize sampling clocks at different locations. After reviewing the techniques for obtaining positive sequence phasors from samples. techniques for clock synchronization are reviewed. Data volume reductions possible with direct measurement of state are examined and static state estimators which incorporate direct measurements are presented. Simulation results for the IEEE 118 bus system are presented.