We’ve had it for while in the USA and Canada. Including lines built in 1932 for testing HVDC using mercury arc valves[1]. https://en.m.wikipedia.org/wiki/List_

We’ve had it for while in the USA and Canada. Including lines built in 1932 for testing HVDC using mercury arc valves[1]. https://en.m.wikipedia.org/wiki/List_of_HVDC_projects https://en.m.wikipedia.org/wiki/List_of_HVDC_projects [1] https://en.m.wikipedia.org/wiki/Mercury-arc_valve https://en.m.wikipedia.org/wiki/Mercury-arc_valve