Load estimation issues in real-time power system state estimation

This paper outlines issues related to load estimation in real-life state estimation for the power grid, particularly related to the phenomenon of “injection dumping”. Each of the issues tend to vary in terms of the actual model conditions but there is an underlying commonality, that being an injection mismatch in the observable system that gets unevenly distributed among loads in weakly or unobservable buses. The paper provides a quick background into the conventional implementation of existing state estimation techniques and explains the factors that cause the phenomenon of injection dumping. The paper then proceeds to outline the methodology of adding pseudo measurements with appropriate weights, and the sources of these measurements to assist in resolving the problem. As real-time network models that run balanced three-phase state estimation continue to be expanded down to the distribution feeder loads, the problem of ensuring reasonably accurate estimates for weakly observable or unobservable load buses becomes increasingly pressing.