Mercury-arc valves Early HVDC experiments based on mechanical, moving contact devices were unsuccessful so pioneers soon turned their attention to the potential of mercury-arc valves. At the end of the 1920s, ASEA embarked on the development and manufacture of static converters and mercury arc valves for voltages up to about 1 kV, and the possibility of developing valves for even higher voltages began to be investigated. In 1933, an experimental valve was produced that confirmed the validity of the principle.
In 1944, Dr. Uno Lamm, "the father of HVDC" successfully operated a rectifier and an inverter in his laboratory in Ludvika, Sweden at a power rating of 2 MW and voltage of 60kV The time was now ripe for service trials at powers higher than those that could be accommodated at Ludvika so a test station, run jointly by the Swedish State Power Board and ASEA. was established in 1945 at Trollhattan and a 50 km power line was made available for service trials title picture