Observability of low voltage grids: Actual DSOs challenges and research questions

Low Voltage (LV) distribution power grids are experiencing a transformation from a passive to a more active role due to the increasing penetration of distributed generation, heat pumps and electrical vehicles. The first step towards a smarter operation of LV electrical systems is to provide grid observability in the control centers. In some countries like Denmark, the rollout of Advanced Metering Infrastructures (AMI) has reached 100%. However, the vast amount of data sent from the smart meters to the control centers stresses the communication network, and complicates the data processing tasks. It becomes unrealistic to provide near real time full observability of the LV grid by applying Distribution System State Estimation (DSSE) utilizing the classical data collection and storage/preprocessing techniques. This paper investigates up-to-date the observability problem in LV grids by providing an updated state of the art on DSSE-AMI based, adaptive data collection techniques and database management system types. Moreover, the ongoing Danish RemoteGRID project is presented as a realistic case study.

I. Introduction

Originally, centralized generation at the transmission level allowed Distribution System Operators (DSOs) to design and operate their systems through a top-down approach [1]. It means that predictable power flows from the transmission systems did not require advanced management and observability resources. Nowadays, at the distribution level, decentralized and unpredictable generation from Renewable Energy Sources (RES) introduces new challenges, such as bidirectional power flows, greater variations on the node voltages and different reactive power characteristics. In fact, the penetration of such devices is on the rise. According to the EU, by 2020 it is expected that RES will meet a 20% in the total energy consumption what in return means that the energy production from such devices in also expected to increase considerably. Moreover, in the EU it is expected that by 2050 Electrical Vehicles (EV) will represent the 10% of the electric share [1].