Re: primary solid/tube

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>


----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Friday, July 12, 2002 5:20 PM
Subject: Re: primary solid/tube


> Original poster: "J Dow by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<jdowphotography-at-hotmail-dot-com>
>
>
>
> Hello folks
>
> Thanks for all the replies for the solid vs. hollow CU primary question.
My
> thanks to Terry, Dan, Gary and the rest
> "Advanced knowledge in these matters is not needed while wandering the
isles
> of Home Depot ;-))" -Terry"  lol so true.lol.
>
> I was fascinated to find out that DC!! Is used in long distance power
> transmission! Wow I thought one could not transmit DC more than a few
miles.
> And that this why we all use Tesla's AC and not Edison's DC. Wow!

Perhaps at the turn of the 19th to 20th century, long distance DC
transmission was impractical, but these days, not so bad.  It's still
expensive though (compared to a conventional AC line, where all you have is
transformers), so you have to have a real good reason:

-crippling stability problems
- intertie between two very dissimilar systems (there's several places where
there's a GW+ link that runs a few hunderd feet.. one's at Itaipu dam
(border between Paraguay and Brazil and they use 50 Hz on one side and 60 Hz
on the other), another is somewhere in Eel River Canada , where it
simplified things.
- reliability (2 wires, but if one fails, you can use "ground" as the other
conductor)
- very long lines (1000's of km) (stability is tough, and you can use 2
wires instead of 3, and so save money on towers, insulators, etc.)
- underground and underwater cables... capacitance and inductance kills you
with AC on these...

The end stations ARE expensive though (wonder what a stack of 1200A GTO
thyristors to handle 1 MV runs? what about the drive circuitry?)

To keep this at least nominally TC related, there is a benefit to us from
all this: It pushes the development of high power semiconductor switching
devices.  There's also a lot of spark research connected with EHV lines, AC
and DC.  DC is particularly troublesome... no current zero crossings to help
quench the arc after a fault.