Such long-distance backbones and interconnections between nations are quickly gaining speed in Europe since the 1980's, as they reduce the risk of blackout and enable savings (a temporarily useless production unit here is used to feed a another nation).

https://en.wikipedia.org/wiki/Synchronous_grid_of_Continenta... https://en.wikipedia.org/wiki/European_super_grid https://en.wikipedia.org/wiki/List_of_HVDC_projects