The European electricity system is facing major challenges to implement a strategy for a reliable, competitive and sustainable electricity supply. The development and the renewal of the transmission infrastructure are central and recognised issues in this strategy. Indeed the transmission system is a complex and strongly interconnected infrastructure that offers a wide range of benefits like reliability improvement, promotion of competitive electricity markets and of economic growth, support for development of new generation and for exploitation of renewable resources. Within this context, the objective of REALISEGRID is to develop a set of criteria, metrics, methods and tools (hereinafter called framework) to assess how the transmission infrastructure should be optimally developed to support the achievement of a reliable, competitive and sustainable electricity supply in the European Union (EU). The project encompasses three main activity-packages: 1) identification of performances and costs of novel technologies aimed at increasing capacity, reliability and flexibility of the transmission infrastructure; 2) definition of long term scenarios for the EU power sector, characterized by different evolutions of demand and supply; 3) implementation of a framework to facilitate harmonisation of pan-European approaches to electricity infrastructure evolution and to evaluate the overall benefits of transmission expansion investments. The expected output of the project is fourfold: - Implementation of the framework to assess the benefits provided by transmission infrastructure development to the pan-European power system. - Preparation of a roadmap for the incorporation of new transmission technologies in the electricity networks. - Analysis of impacts of different scenarios on future electricity exchanges among European countries. - Testing and application of the framework for the cost-benefit analysis of specific transmission projects.