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DANMARK, SKAGERRAK4. Vy av nybyggda HVDC anlŠggningen utanfšr Viborg, Danmark.

Foto: Gustav MŒrtensson
Case Study


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

The Skagerrak HVDC transmission system comprises several HVDC links which together provide a total of 1,700 MW transmission capacity between Kristiansand in southern Norway and Tjele on Denmark's Jutland peninsula. The link is owned by Statnett in Norway, and in Denmark.

Skagerrak 1&2 rated 500 MW was commissioned in 1976-77 and Skagerrak 3, rated 440 MW, became operational in 1993. The latest Skagerrak project was awarded to Hitachi Energy in 2011, and comprises a fourth link using HVDC Light® technology which operates in a bipole mode together with the Skagerrak 3 HVDC Classic link and a control system upgrade of the latter. This is the first time an HVDC Classic and an HVDC Light® link are tied together in such a bipole configuration. This is possible because of Hitachi Energy's advanced MACH control system, which was also used for a Skagerrak 1-2 upgrade in 2007.

The new link boosts transmission capacity between the mainly hydroelectric-based Norwegian system and the wind and thermal power-based Danish system by an additional 700 MW with a voltage rating of 500 kV. It enables both networks to add more renewable energy to their energy mix, and to use electricity more efficiently.

The system helps overcome distance and grid constraints while ensuring robust performance, power quality and minimal electrical losses. In the rare case of a power system outage, the technology’s ‘black-start’ capability allows for a fast network restoration using power from the other end of the link. These factors were essential in the selection of the HVDC Light® technology for the fourth Skagerrak HVDC link.

Main data
Commissioning year: Pole 4 and upgrade pole 3: 2015
Pole 1&2 upgrade: 2007
Pole 3: 1993 
Pole 1&2: 1976-77
Configuration: Asymmetrical monopole
Power transmitted: Pole 4: 700 MW
Pole 3: 440 MW
Pole 1+2: 500 MW
Direct voltage: Pole 4: 500 kV (HVDC Light®)
Pole 3: 350 kV (HVDC Classic)
Pole 1&2: 250 kV (HVDC Classic)
Application: Interconnecting grids; Overhead transmission lines for HVDC; Upgrades