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'Voltage drops'
2005\08\13@060056 by Vasile Surducan

face picon face
On 8/11/05, Jinx <spam_OUTjoecolquittTakeThisOuTspamclear.net.nz> wrote:
> > No, all fixed wiring is solid core in the UK (known as "twin
> > and earth").  Stranded wiring is only use for appliance "flex"
>
> Does the "skin effect" come into play with solid (single strand)
> cable ? Undoubtedly the power company engineers know a
> heap more about this than I do, just wondered if there was any
> significant advantage to using multi-strand (Litz) cable, cf power
> transmission over long distances by DC rather than AC

Joe, aerial lines are using only flexible cable. In the center there
is a good mechanical wire while surrounded by good electrical
conductor wires (aluminum because is cheaper). So the skin effect at
very high current (that's the only one it count at low frequencies) is
already known at the manufacturing time.

DC versus AC for long distance fails because of too complicated (and expensive)
conversions methodes at the lines ends.

cheers,
Vasile


>
> --

2005\08\13@123712 by Herbert Graf

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On Sat, 2005-08-13 at 13:00 +0300, Vasile Surducan wrote:
> DC versus AC for long distance fails because of too complicated (and expensive)
> conversions methodes at the lines ends.

I'm not sure what you mean by "fails". Very high voltage DC lines
certainly exist (I would even say common in some areas). For example, in
Quebec, Canada there is a line going from a hydroelectric generating
station in James Bay to I believe Montreal, and it's a very high voltage
DC line.

While it is more complicated and costly, DC transmission certainly has
it's benefits, especially when long distances are necessary.

TTYL

-----------------------------
Herbert's PIC Stuff:
http://repatch.dyndns.org:8383/pic_stuff/


2005\08\13@150938 by David Van Horn

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-----Original Message-----
From: .....piclist-bouncesKILLspamspam@spam@mit.edu [piclist-bouncesspamKILLspammit.edu] On Behalf
Of Herbert Graf
Sent: Saturday, August 13, 2005 11:37 AM
To: Microcontroller discussion list - Public.
Subject: Re: Voltage drops

On Sat, 2005-08-13 at 13:00 +0300, Vasile Surducan wrote:
> DC versus AC for long distance fails because of too complicated (and
expensive)
> conversions methodes at the lines ends.

I'm not sure what you mean by "fails". Very high voltage DC lines
certainly exist (I would even say common in some areas). For example, in
Quebec, Canada there is a line going from a hydroelectric generating
station in James Bay to I believe Montreal, and it's a very high voltage
DC line.


It failed in terms of what was available in 1920 to deal with conversion
of DC to other voltages.  In order to go long distances, you had to use
high voltages to get past the I^2R losses, and those voltages were not
workable in reasonable equipment.   AC allowed you to use simple
transformers to make local low voltages for equipment. Tesla saw this,
and had the AC motors to make it work. I think Edison saw this, but only
after he had put his name on the DC system, and he wasn't going to back
down on it.




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