Uncertainty sources affecting voltage profile in Distribution System State Estimation

Electrical distribution systems are usually poorly monitored networks with few measurement devices installed on the field. The significant changes affecting the distribution grids in last decades, mainly due to the increasing penetration of Distributed Energy Resources (DERs), call for a smarter monitoring and control of such networks. In this context, the accuracy of the electrical quantities provided by distribution system state estimators plays a key role for management functions. This paper focuses on the accuracy of the voltage profile obtained by means of Weighted Least Squares (WLS) estimators. A mathematical analysis is proposed, highlighting the factors affecting the accuracy of the estimated voltages. The proposed analysis shows how the accuracy of the estimated data varies depending on the chosen measurement system. Tests on a 95-bus network validate the theoretical analysis and show the impact of measurement uncertainties in different scenarios. The presented considerations provide useful information about the measurement system needed to achieve fixed accuracy targets.