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HVDC Boosting power with HVDC Light® Fast-track solution increases capacity of existing infrastructure to help meet EU emissions targets Hydro Wind Solar AC Europe`s challenge is to find environmentally acceptable technologies that can increase power capacity and remove the bottlenecks in existing transmission right-of-ways, creating a stronger, smarter continental power infrastructure. To cope with rising electricity consumption and enable the integration of more renewable energy sources (RES) into the energy mix, Europe must strengthen its transmission grids and improve controllability. This is especially true as large offshore wind parks under development in the North Sea region come online. The integration of European transmission systems is part of a ten year plan driven by 42 transmission system operators (TSOs) comprising the European Network of Transm ission System Operators for Electricity (ENSTO-E). EU legislation is driving development of a Pan-European grid, with concerns about security of energy supply, competitive and integrated continental power markets, and the secure integration of new generation sources to help meet emissions reduction targets (EU 20/20/20). In addition to managing more unplanned and intermittent electricity production, Europe needs new power corridors, but costly overhead lines are time-consuming to build and enjoy little public acceptance. The challenge is to install fast-track solutions that can transmit several GW (gigawatts) of bulk electricity and remove local bottlenecks, without protests and delays. DC One solution is HVDC (high-voltage direct current) Light, VSC (voltage source converter) technology, which increases capacity and improves controllability of existing transmission grids. Converting existing AC (alternating current) lines to DC (direct current) can double or triple power capacity with minimum interruption. Where AC solutions are predominant, power can still be transmitted by using high-voltage AC or DC technologies. HVDC technology was introduced about 60 years ago to transmit electricity underwater from mainland Sweden to the island of Gotland, and Nordic countries have built similar connections since then. Planned new interconnectors will help the Pan-European grid integrate large hydroelectric resources in Scandinavia and large wind power resources in northwestern Europe. In 1984 the Itaipu interconnection in Brazil introduced long-distance HVDC hydroelectric overland transmission, rated at ±600 kV (kilovolts). Voltage for HVDC Classic CSC (current source converters) increased to ±800 kV in China, and now transmits more than 7000 megawatts (MW) of electricity over long distances with very low losses. Increased power by converting 400 kV AC to DC System study (feasibility) System study (verification) Identify AC line and substations Mapping of line and substations Suitable DC line configuration Line & substation design Suitable DC converter AC/DC line conversion Consequence study AC/DC substation conversion MW 7000 Improvement of parallel AC-grid 6000 Transmission 5000 line power 4000 2000 1000 0 AC DC 400 DC 500 kV By converting a 400 kV transmission line to 400 kV or 500 kV DC it is possible to significantly increase power transfer. How much has to be investigated from case to case. ABB introduced HVDC Light VSC in 1997, focusing on moderate voltages and power ratings for cable applications. Today, there are more than ten systems in operation including cable and overhead line solutions. DolWin2, the world’s largest offshore wind farm connection, increases the HVDC Light voltage rating to ±320 kV and 900 MW. A modular concept enables voltages as high as ±500 kV, and is an opportunity to convert existing 220 kV and 400 kV AC lines to DC at even higher voltage capacities. This can double or even triple the power capacity of existing power corridors, and also improves the parallel AC system: a smart fast-track solution to increase grid transfer capability. Converting one 400 kV line or a double circuit 220 kV line from AC to DC can increase transmitted power by more than 1000 MW. Converting a double circuit 400 kV line (2x3 conductors) to a triple 500 kV DC line (3x2 conductors) can increase transmitted power by 5000 MW taking into account more efficient use of the parallel AC-system. Step one is a feasibility study to identify a transmission line and substation suitable for AC/DC conversion. Based on this, a potential DC line configuration is established and possible voltage and current values calculated. The type and rating of DC converter is then chosen. A consequence study later examines load, reliability, induction effects, corona, magnetic fields and power quality. In addition to technical investigations, a commercial study calculating costs and benefits is also necessary. The decision to proceed is followed by a verifying system study, and the transmission line and substation are mapped to create a detailed design. Work must be carefully planned and performed to minimize interruption time of the existing line and substation. The main advantage of an AC/DC conversion is the grid`s increased power transfer capability, accomplished with minimal environmental impact, investment cost and time. Additional benefits include: −− −− −− −− −− Improved power flow control Improved network reliability/redundancy (bi-pole) Easier to establish dynamic current rating Minor modifications possible to existing live lines Underground installation easier in sensitive areas If proper preparations are done (line insulators changed on the live line and converter station and substation bypasses built while still running AC) the effective interruption can be less than one month. The applications suitable for an AC/DC conversion include: − − Connecting increased remote generation, such as wind power, to load centers − − Increase capacity between interconnected energy markets − − De-bottlenecking congested areas by integrating DC links in the AC grid For more information please contact: ABB AB Grid Systems – HVDC SE-771 80 Ludvika, Sweden Tel: +46 240 78 20 00 Fax: +46 240 61 11 59 www.abb.com/hvdc POW-0077 rev.0 3000