This Summary Report briefly describes the main themes and results achieved in 2016 by Project A.4 (‘Evolution and Development of Distribution Networks’).

In recent years, there has been an increasing diffusion of Distributed Generation (DG), especially from non-programmable renewable sources (NPRSs), coupled with the growth of some technologies replacing other carriers (e.g., electric vehicles, heat pumps). This requires an evolution of the distribution network function, which becomes a ‘facilitator’ of new market mechanisms, while continuing to ensure system resilience, continuity and quality of supply. There is agreement that market participation should be expanded to generation from non-programmable renewable sources and DG for ancillary services, and prospectively for loads and storage systems as well. However, the roles of the different players and the mutual interactions are yet to be defined, with particular reference to how the distribution system operator (DSO) can reconcile the provision of services (of a global nature) by distributed generation (DG) with the (local) needs for quality of supply.

In addition, the significant increase in the penetration of renewable energy sources (RES), often through small-scale generators connected to the distribution grid, may prospectively increase the operating issues of the power system. As an alternative to the permanent or temporary installation of batteries pending eventual enhancement of the distribution grid, the possibilities offered by the innovative use of small-scale hydroelectric pumping were investigated.

Finally, taking into account the inevitable evolution of distribution networks towards ‘Smart Grid’ solutions, it is important to prepare supporting tools to assess the impact of such projects.

All the above has prompted the expansion of the scope covered by the 2015 Annual Implementation Plan with the inclusion of two additional topics that were previously marginally addressed by other System Research projects: the evaluation of construction costs and benefits of small pumped storage plants and the preparation of support tools for the impact analysis of Smart Grid implementations.