A new electricity transmission connection between Finland and Sweden, Fenno-Skan 2, will be commissioned at the end of this year. The laying of the subsea cable for this interconnector is currently underway outside Rihtniemi in Finland. The new high-voltage direct current transmission connection will reinforce the Nordic electricity market and the system security of the transmission grid.

Fenno-Skan 2 is an 800 MW and 500 kV electricity transmission connection between Finland and Sweden. The total length of the link will be approx. 300 km, of which the actual submarine cable will account for some 200 km. The project costing a total of 315 million euros is being implemented jointly by transmission system operators Fingrid Oyj and Svenska Kraftnät in Finland and Sweden respectively.

There are converter stations at both ends of the link, used for converting direct current to alternating current and vice versa. The submarine cable will be connected to the Finnish transmission grid at the Rauma substation. In Sweden, the connection point to the Swedish grid is the Finnböle substation built north of Stockholm.

The submarine cable will be laid on the seabed in two sections of approximately 100 km each. One of these has already been laid in the sea from the coast of Sweden. The cable-laying work in Finland outside Rihtniemi started July 15. The weight of this campaign is 5,800 tons, which is equivalent to the mass of more than 200 trams used in Helsinki. The carrying capacity of the cable ship c/s Nexans Skagerrak is 7,000 tons.

“The installation work in Finland is a little easier than in Sweden, since the land portion of the cable is only about 300 m. On the Finnish side, the cable will be buried in the seabed in a ditch about one m deep. This protects the cable from mechanical damage and minimizes disadvantage inflicted on commercial fishing,” said Fingrid’s CEO Jukka Ruusunen in Rauma.

The laying of the cable outside the coast of Finland will take about a week. The cable will be connected to the cable launched from the Swedish side halfway through the interconnector.

Enhanced market functioning and improved system security
Fenno-Skan 2 responds to the needs of the electricity market and transmission system security. The Nordic transmission system operators have jointly specified the foremost congestions in Nordic electricity transmission. These congestions are to be removed so as to promote the electricity market and system security. Fenno-Skan 2 is one of the most important new transmission connections. The submarine cable will increase the electricity transmission capacity between Finland and Sweden by 40 per cent and integrate the electricity market in the two countries even more closely together.

“The new interconnector will reduce temporary differences in the price of electricity resulting from the splitting of the electricity market, and reduce the losses in the Nordic transmission grids. The connection will also improve transmission system security. For example, last winter we had technical problems in submarine cables during the coldest period,” Jukka Ruusunen said.

Fenno-Skan 2 in brief

• capacity 800 MW, voltage 500 kV

• transmission length 299 km, of which 103 km is overhead line and 196 km submarine cable

• converter stations in Rauma, Finland, and in Finnböle, Sweden

• commissioning at the end of 2011

• co-operation project between Fingrid and Svenska Kraftnät

• submarine cable manufacturer: Nexans Norway AS

• converter station manufacturer: ABB AB

• total cost of project: 315 million euros