What is power system state estimation and how does it work?

State estimation processes redundant real-time measurements to determine the most likely system state (voltage magnitudes and angles at all buses). It uses weighted least squares to minimize measurement residuals while satisfying power flow equations. Bad data detection identifies faulty measurements using normalized residuals. Observability analysis ensures sufficient measurements exist for unique solution. State estimation enables real-time security analysis, economic dispatch, and provides input for energy management systems. PMUs improve estimation accuracy and speed.