The Gotland HVDC Link was the world's first commercial HVDC transmission link, using the first submarine HVDC cable. It connected the Island of Gotland to mainland Sweden via a 96 km mass-impregnated cable. Swedish manufacturer ASEA produced the link for Vattenfall, the state-owned utility. The project used mercury-arc valves for the 20 MW/100 kV HVDC converters, developed by an ASEA-Vattenfall team led by Dr. Uno Lamm.