[cesis]

There are many already existing HVDC transmission lines, e.g.:

https://en.m.wikipedia.org/wiki/File:HVDC_Europe.svg

[giva]

I think they are mostly used when an AC trasmission is impossible: AFAIK only synchronized grids can be connected by AC.

https://upload.wikimedia.org/wikipedia/commons/6/6d/Electric...

[emilfihlman]

You are entirely correct. Power between different AC regions is mostly transferred using HVDC-links because it avoids synchronisation requirements between them.

Additionally the capacitive losses of an undersea HVAC cable are prohibitive, leaving only HVDC as an option.

[emilfihlman]

You'll notice almost all of these are undersea cables. HVDC connections are used there because you can't really hang air cables over the ocean and the capacitive losses of HVAC cables under the sea makes them prohibitive.