Distribution state estimation based on voltage state variables : Assessment of results and limitations

Distribution networks are facing significant technical constraints that must be resolved at minimum cost: regulatory and customer pressures to improve reliability of supply, reduction of losses and the technical challenges related to the connection of an increasing amount of distributed generation. The use of new approaches is therefore being encouraged to develop cost-effective solutions often leading to the concept of Active Management. However, the lack of monitoring in present distribution networks is a barrier to the implementation of the corresponding automation functions. On the other hand a full monitoring of the distribution network is not economically realistic. Therefore, there is a need for intermediate solutions such as the one presented in this paper: EDF R&D has developed a distribution state estimator (DSE) based on voltage state variables. Such algorithm is expected to provide quasi-real time system supervision of voltages and power flows which are required as inputs of Distribution Management System (DMS) functions. Even if based on techniques applied to transmission networks, the requirements and performances of DSE are different and adapted to distribution needs. The paper discusses the limits of such approach and proposes thumbed rules for sensors placement as well as research perspectives to overcome these limits.