This article presents the modifications and improvements that have been included over the classic formulation of the state estimation to be able to run in real networks with large power distribution systems. Improvements include a new penalty term that keeps bus consumption or power generation within an allowed band and the inclusion of dynamic elements such as voltage regulators and capacitor batteries. A complete algorithm is presented that is capable of operating on large power systems in near real time. This algorithm and the results have been tested with numerous cases of real distribution networks covering large geographical areas, obtaining very good results and demonstrating the enormous usefulness of this approach.