The Elbe-project was the name of the first commercial static high voltage direct current transmission system in the world, based on mercury arc valves.

Experimental installations between Weittengen and Zurich, and Charlottenburg and Moabit, Berlin, were demonstrated between 1933 and 1942. Contracts were signed with AEG and Siemens in 1941, and construction began of a bipolar direct current line from the Elbe power station near Dessau, to Berlin-Marienfelde, in 1943. The line was designed to transmit 60 megawatts using a symmetrical bipolar operating voltage of +/- 200 kV. Two single-core earth cables were used, (a piece of the cable used can be seen in the Deutsche museum, Munich).

The system was never put into service owing to the chaos in Germany at the end of WWII.The situation in post-war Germany allowed the Soviets to dismantle the system and reuse it in the building of a 100 kilometre long 200kV monopolar high voltage direct current line with a maximum transmission rating of 30 megawatts between Moscow and Kashira, in 1951. Nowadays the high voltage direct current line between Moscow and Kashira is shut down.

Reference

[Power Electronics in Europe]