Skagerrak HVDC Interconnection

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An excellent example of the benefits that can be achieved through interconnection.

An electric DC power transmission between Norway and Denmark (using the Thury system) was proposed as early as 1922. But it lasted 54 years until the first 500 MW war realized in 1977. Today the Skagerrak link has three cables: Skagerrak 1&2 with 500 MW (1976-77) and Skagerrak 3 (1993) with 440 MW. The link goes between Kristansand in southern Norway and Tjele on Denmark's Jutland peninsula. The link is owned by Statnett in Norway, and Energinet.dk in Denmark.

Link to: Overview of the Scandinavia - Northern Europe interconnections where the reasons for this link are described.

Aerial overview of Tjele converter station with the converters for Pole 1&2 to the left and Pole 3 to the right.

The converter stations for Skagerrak 1&2 (1976-77) were the first stations to employ the modern circuitry and station design that is employed even today. The first stations with thyristor valves were designed according to the principles adopted for mercury arc valve stations. But ABB adopted new design principles for the converter stations of the Skagerrak 1&2 link:

Valve hall in the first Skagerrak link	twelve pulse converters quadruple thyristor valves no 5th or 7th harmonic filters on the AC-side converter transformers close to the valve-hall with the valve-side bushings in the valve-hall The Skagerrak 1&2 link was the first one to employ ABB´s second generation of air-cooled valves (which also were used in the CU and Inga-Shaba transmissions).

When Skagerrak 3 (1993) was built it was decided to reconfigure the existing bipole so that Pole 1 and Pole 2 operate with the same current direction. Thereby achieving a better current balance, since the Pole 3 has a higher current than Pole 1 and 2.


Simplified single line diagram of the entire Skagerrak scheme.

The converter stations of Pole 3 was the fist in the series of ABB cable projects during the 1990's that also includes Baltic Cable, Kontek and SwePol.

Main data
Commissioning year:	Pole 1&2: 1976-77 Pole 3: 1993
Power rating:	Pole 1+2: 500 MW Pole 3: 440 MW
No. of poles:	3
AC voltage:	Pole 1&2: 300 kV (Kristiansand), 150 kV (Tjele) Pole 3: 300 kV (Kristiansand), 400 kV (Tjele)
DC voltage:	Pole 1&2: 250 kV Pole 3: 350 kV
Length of DC submarine cables:	127 km
Length of DC overhead line:	113 km
Main reason for choosing HVDC:	Length of sea crossing, asynchronous link.