SUPPLY OF ISLANDS THROUGH LONG DISTANCE SUBMARINE CABLES: PROBLEMS AND PROSPECTS (CASE STUDY: CYCLADIC INTERCONNECTION)

摘要

This paper describes a number of topics concerning the interconnection of a complex of islands to a bulk power system. This report reflects the results came out from a working team established by the Greek Ministry of Development to survey the technical and economical feasibility of a future interconnection of the northern part of the Cycladic complex to the Greek mainland. The main technical questions faced during this work concern: The long distance of interconnections in conjunction with the high capacitance of submarine cables. The alternative available cable technologies (low pressure oil filled, mass impregnated paper and cross-linked polyethylene) have been considered and analyzed. The advantages and disadvantages of DC vs AC connections as far as: Reactive compensation requirements; Voltage regulation at the receiving end of the interconnection; Installation issues; Maturity and references of available technologies. Operational issues in case of DC link such as: Selection of DC technology (classic thyristor-based Line Commutated Converters (LCC) vs Voltage Source Converters (VSC) based on IGBT's); Investigation of the possibilities for parallel operation of DC link(s) with the AC system; Mode of operation of the DC link (power or frequency regulation) with regard current operation practices. A number of alternative interconnection schemes have been analyzed with respect to static security taking into account the current Grid Code provisions. The economic feasibility of above scenarios has been analyzed taking into account: The today's high cost of electricity supply in the islands; The generation costs of the bulk interconnected system of the mainland; The cost of new transmission projects needed to establish the interconnection; The repercussions of the interconnection to the bulk system's economics.