The first HVDC submarine cable was installed for the Baltic
Island HVDC project in 1954. It also used the MI insulated
cable to transmit 20 MW of power at 100 kV voltage levels and
over a 100 km distance between the Baltic island of Gotland
and the Swedish mainland [27], [28]. The cable was then
expanded to 150 kV and 30 MW in 1970, before finally going
out of commission in 1986. The Baltic Island HVDC project
was the first to use the thyristor valve technology [29].