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Project advancing - milestone achieved
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Major milestone or critical setback
Gotland 1, the first HVDC Gotland link, entered commercial operation in March 1954, transmitting up to 20 MW at 100 kV over a roughly 96–98 km mass‑impregnated submarine cable between Västervik on mainland Sweden and Ygne on Gotland. The converter stations, using mercury‑arc valves developed by ASEA for the state-owned utility Vattenfall, made this the world’s first fully commercial high-voltage DC submarine transmission link.