Fingrid Oyj has made an investment decision to build a new Naantalinsalmi 110-kV substation. The new substation makes it possible to connect the new HVDC submarine cable between Åland and Continental Finland. The new substation will also replace the existing 110-kV switchgear located in Naantali power plant. The old switchgear does no longer fulfill the operational reliability demands of Finnish national grid.
The new substation will be built to approximately 1 km distance from the existing substation just beside the 110-kV power line route. The 110-kV switchgear will be 2 main bus + 1 transfer bus air isolated type including 12 feeder bays and 1 bus breaker bay. The future growth expectations in energy production and consumption on Turku region has been taken into consideration on space reservations of the switch gear. The 11.2 hectare substation site also enables to extend the substation with a 400-kV switchgear, power transformers and a reactor plant. The estimated total cost of the investment is 8.8 million euros.
Building of the substation will be launched on spring 2013 and the station will be completed on 2015, parallel with a HVDC converter station built on neighbor real estate by Kraftnät Åland. The transmission system operator on Åland, Kraftnät Åland Ab, will build a submarine cable to Continental Finland. The cable will come into operation late in 2015. The interconnection will be connected to Fingrid's transmission grid in Naantali.
The transmission capacity of the submarine cable is 100 MW. The interconnection is built to improve power system security on Åland. The technical transmission capacity between Central Sweden and Continental Finland will be increased at the maximum 80 MW to both directions, as the current interconnection capacity of between Sweden and Åland is 80 MW.