Pat McBride wrote:
However, DC doesn't really work all that well over long distances, measured
in miles (or KM) and has to be boosted every so many miles. The power lines
in BC that we're talking about go for about 500 miles or so, use 3-phase
power, and therefore it's cheaper in cost of transmission wire to use AC.
The newest systems use DC transmission at 500 KV or so. The higher the
voltage, the less the power loss per mile, at least as far as resistance
losses is concerned, and those are the ones that dominate. This loss is
exactly the same with AC or DC, only the voltage matters, not whether it
alternates or not. Induction losses are a lesser but still very
significant factor. AC losses are of two types, simple induction
losses, where conductive materials in the vicinity of the transmission
line develop local currents which are parasitic, like the farmer's
coils, and the second is the tendency of the lines to act as a huge
radio antenna radiating 60 Hz into space. That is also power wasted
that doesn't occur with DC. The reason that DC was not used until
recently is simply that converting DC back into AC so that transformers
could step it down was very expensive, and therefore impractical. Solid
state oscillators have greatly lowered the cost of doing this and
therefore made it practical.
-----Original Message-----
From: Robert Derman [mailto:[EMAIL PROTECTED]
Sent: 2008/05/27 15:11
To: [email protected]
Subject: Re: [social] I am not receiving anything from this list
Ian Lynch wrote:
On Tue, 2008-05-27 at 13:14 -0500, Robert Derman wrote:
This is why a lot of the high power transmission lines now use direct
current rather than alternating current. There was just too much
induction loss.
Snag with transformers then? I would have thought the additional cost of
stepping up and down voltage would have made it uneconomic for general
use but then again technology changes so maybe I'm just out of date :-).
Ian
Solid state oscillators turn it back to AC at its destination so that
transformers can step the voltage down. The cost of doing this is far
less than the value of the energy lost by AC losses.
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