The 20 MW, 100 kV Gotland 1 HVDC link from 1954 was the first commercial HVDC transmission in the world. The converter valves were mercury-arc valves. In 1970, the stations were supplemented with thyristor valves which were connected in series with the mercury-arc valves. The voltage was raised to 150 kV and the transmission capacity to 30 MW.
It was the first time thyristor valves were used in a commercial HVDC transmission in the world. Read more about Gotland 1 in: The early HVDC development
In 1983, a new cable was laid between the inverter station near Västervik on Sweden's west coast and Ygne station on Gotland. Gotland 2's rated voltage was 150 kV and transmission capacity 130 MW and the converters were built up of thyristor valves. Gotland 2 and Gotland 1 operated independently and together met Gotland's power needs. Fossil fuel generation on the island was shut down and used only for reserve generation.
Increasing demand and concern about supply safety led to a decision in 1985 to build another HVDC link to Gotland, the Gotland 3, which usually works with Gotland 2 to form a bipolar link but can also work independently. The total transmission capacity is 260 MW (max. 320 MW).
The original cable and terminal equipment for Gotland 1 were taken out of service and dismantled in 1986 when Gotland 3 was built. The owner of the link is Vattenfall.