transmission systems Paola Bresesti*, G. C. Stevens**, B. Philphot** , P. Sinclair***, P. Adam**** Pietro Antonelli*****, Enrico Carlini*****, W Kling****** CIGRE’ 2006 Session 41 Technical Exhibition Exposition Technique Parigi, 27 Agosto 1 Settembre 2006 * CESI RICERCA ** UNIVERSITY OF SURREY, UNITED KINGDOM *** INDUSTRIAL ECOLOGY SOLUTIONS, UNITED KINGDOM **** RTE FRANCE ***** GRTN ****** TEET NETHERLANDS Under the acronym “HVDC Project”, the European Union has financed a project to provide a methodology and associated software to assess the potential technical, economic and environmental benefits and impacts of HVDC embedded in the largely HVAC electrical power transmission system of the European network. The purpose of this paper is to present one of the key outputs of this project: the “Life cycle Environmental and Economic analysis of Transmission Systems” (LEETS) methodology and model, its implementation in a software, and its application to case studies. Three case studies covering a wide range of purposes have been used to test and validate the model: an island to mainland connection, a European inter-State interconnection, and the connection of an offshore wind farm to a national grid. The model considers a wide range of needs related to environmental concerns: public acceptability of new schemes, often involving new technologies, with debates that involve “subjective risk”; the need for national and local authority, agency and public awareness raising and learning about new scheme proposals; the need for integration of environmental and economic factors in investment decision-making; and the need for a life cycle approach to investment in, and the operation of, HV links and connections. It is likely to be used by project and system planners in the early stages of a project. Initial implementation therefore focuses on having a transparent and comprehensible tool for those with industry expertise. The approach may also be used to assist in communicating projects outside the industry. It offers the possibility to choose optimisation goals: minimise cost, minimise environmental impact, or reduce cost and environmental impact. The paper describes the main characteristics of the model as well as the software specifications: system boundaries (environs, systems and functional units), system activities and objects (economic and environmental properties), component hierarchy, factors which can be considered (environmental, economic, investment criteria). An open architecture allows the participation of different users who have different views on what may be important to model, in accordance with different measures of subjective risk and different views on the most important economic and environmental factors. KEYWORDS Transmission system, HVDC, HVAC, life cycle, environment, economic assessment, LEETS