The mid-1970s saw the completion of further projects: The Skagerrak link be tween Norway and Denmark, Inga-Shaba in the Congo, and the CU Project in the United States. The converter valves in these projects were air-cooled. The Pacific Intertie was also extended twice in the 1980s, each time with thyristor converters, to raise its capacity 3,100 MW at t 500 kV.