Offshore Power Transmission: Submarine high voltage transmission alternatives

Abstract

Offshore power transmission is becoming an increasingly important issue. To moderate climate change, world leaders have set environmental goals that will be very difficult to reach without renewable power production and the removal of production units with high emissions. Wind power and electrification have been the focus in this report. Plans for the expensive wind power are already moving offshore. This report has made an attempt at suggesting a guideline for well-suited transmission systems, for wind power projects located at a distance in order to make them more economically attractive. Another emphasis has been to find the most suitable transmission system for gas turbines at offshore installations. As expected, the use of alternating current is best suited at shorter distances. At longer distances this system is still feasible up to 350 km, but losses will be high and there will be limited power available. A conventional thyristor-based direct current system will therefore be an attractive option for high power ratings and long distances. On the other hand, direct current based on voltage-source converters is considered more expensive, but has an improved control of reactive power and is therefore preferable to the conventional direct current system. To determine which system has the best design, one has to consider each case individually.