This paper discusses the state of the art in electric power system state estimation. Within energy management systems, state estimation is a key function for building a network, real-time model. A real-time model is a quasi-static mathematical representation of the current conditions in an interconnected power network. Tills model is extracted at intervals from snapshots of real-time measurements (both analog and status). The new modeling needs associated with the introduction of new control devices and the changes induced by emerging energy markets are making state estimation and its related functions more important than ever.882262282