Hi Gents, HVDC has been used a lot with the development of HV rectifier and inverter devices. Plenty of +/- 500KV Dc on the western seaboard of the US (saves having earth currents).
Our own cross channel link and some other UK schemes use + and - 250KV DC links. The DC link saves the problems that would occur if we tried to synchronise the UK grid to the rest of Europe.
SWER is also used in rural Australia, but at 132KV 50Hz.
Note that on long lines and high voltages losses are very much lower using Dc instead of AC. These tend to be bulk feeder lines or interstate interconnectors.