wqwDavid Nebenzahl wrote:
On 6/1/2008 3:17 PM George spake thus:

DC high voltage transmission lines have lower losses and are less
expensive to build. They use solid state convertors at each end. 500
kV was the max for a while and I know the Canadians have a line in
service for at least 20 years that operates at 735 kV DC and I read
that the Chinese recently started construction of a 800 kV DC
transmission line.

Wow; so that old Tesla-Edison debate *isn't* settled science like
everyone wants us to believe, eh?

Well Edison wanted to transmit at the the same voltage it was going to
be used at. AC made it possible to transform to a higher voltage, and
less loss because there is less i^2 * r loss (double voltage = half
current for same power) I think Tesla would approve of the current
generation HVDC lines, remember the end distribution is still AC.

Got any good reading links on this?

I'm sure there's a good bit on the net.


I'm curious. And, in a nutshell, why
does DC have lower losses? (Not disputing, just curious.)

Advances in semiconductors and circuit breakers made HVDC possible.

You have a higher peak voltage with AC, so you will have more corona
loss. For underground cable, you'll have much less capacitive loss.

For long lines HVDC has a lot of advantages. Higher capacity, lower
losses and a smaller footprint because you have less lines.

Also, it makes it easier to sync power grids as the different power
generators don't all have to be in the same phase. That can be a big
issue and is why restarting a down generator or grid can take a long time.

Jeff