State estimation for low voltage distribution grids

This chapter discusses the subject of distribution system state estimation (DSSE) in low voltage distribution grids (LVDG). In theory, DSSE schemes developed for medium voltage distribution grids (MVDG) are also applicable to LVDGs because of their similar characteristics. However, several limiting factors exist in LVDGs that can severely impact the DSSE performance. First, the measurement infrastructure in LVDGs is lacking with a limited sensor deployment and an absence of communication between the end consumers and the operator. In addition, scarce measurement devices and a slow reporting rate from smart meters with asynchronous measurements render most LVDGs unobservable. Second, there is a lack of reliable and accurate system-related information. This includes information about the topology, parameters and equipment used in any given LVDG which results to a system model with considerable uncertainty. Third, most DSSE methodologies developed for MVDGs are for three-wire networks or four-wire networks with the neutral wire multigrounded. This allows simplifying the problem formulation as the neutral voltage can be approximated to 0 V. In LVDGs, this assumption typically does not hold, and the non-zero neutral voltage has a detrimental impact on the operation of the classical DSSE. These limiting factors along with their impact and mitigation strategies in order to develop adequate DSSE solutions for LVDG are discussed in this chapter.