Power flow based indices for the coordination of transmission and generation system planning

This paper deals with one of the issues consequent on the recent restructuring of the electricity industry: the lack of coordination between generation and transmission system development. Indeed, in this new environment the planning of these two systems is driven by different objectives, resulting in a possible conflict between economics and security. The nodal index called Weighted Transmission Loading Relief (WTLR), recently proposed in literature, seems to be able to supply clear information about the impact of generation and transmission system investments on network security. Therefore, the authors of this paper have developed an automatic procedure to calculate and represent graphically these indices. The procedure has been applied to a detailed model of the Italian EHV network with reference to a summer peak load condition at the projection horizon of the year 2013, in order to highlight the various kinds of information which the above mentioned indices can supply.