When I was looking for a picture of a HVDC power line I stumbled on a report about DC distribution in buildings.
It's from the Swedish institute "Elforsk" ("El" means electricity and "forsk[ning]" research. You can figure out the rest)
Anyway, the idea put forward was a 350 VDC network to replace existing 230 VAC. In 33 pages they conclude that it would work but cost a lot of money. (This was intendend for a residential area where construction just finished here in Stockholm. The report is a few years old.)
Apparently, there were earlier ideas about a 400 Hz network in another residential area. (Never built)
I learnt something else: Submarines have standard 220V and 440V 3-ph 60 Hz systems.
I will provide the link, but there isn't even an abstract in English. Sorry! Link
[This message has been edited by C-H (edited 01-09-2006).]