Konti-Skan

In 1965 the first pole of Konti-Skan went into service with mercury arc valves, a technology that has all but vanished from power grids. It could carry up to 250 MW at 250 kV. That equipment ran until 15 August 2006, when it was taken out of operation and replaced with thyristors rated at 350 MW, according to the Konti-Skan article.

The route crosses the Kattegat by way of the island of Læsø. From the converter station at Vester Hassing, near Aalborg, a 34 km overhead line runs to the coast, a 23 km submarine cable reaches Læsø, and a 17 km overhead line crosses the island before the next sea section to Sweden. On the Swedish side the two poles originally had separate converter stations, at Stenkullen for the first and Lindome, south of Gothenburg, for the second. The remaining parts of the old Stenkullen line were dismantled in 2012.

The second pole, Konti-Skan 2, was added in 1988 and was built with thyristors from the start, carrying 300 MW at 300 kV according to Hitachi Energy, which supplied it as ABB; Wikipedia gives 285 kV. The ratings of the two poles add up to 650 MW, but Svenska kraftnät states the current capacity of the link as 715 MW; the figures above follow the operator.

Energinet and Svenska kraftnät run it jointly, and ABB supplied the cable.

Its time is running out. Svenska kraftnät says both poles are ageing and expected to reach the end of their technical life in the mid-2030s, and a replacement, Konti-Skan Connect, is planned for 2036. By then the route will have carried HVDC for more than seventy years.