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Re: Vegas pole pigs can't take the heat (fwd)

---------- Forwarded message ----------
Date: Fri, 6 Jul 2007 15:23:09 -0700 (PDT)
From: G Hunter <dogbrain_39560@xxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: Vegas pole pigs can't take the heat (fwd)

This is a puzzle.  I'm no engineer, but I think pole
transformers are protected from overload by a
"blowout" fuse or a mechanical recloser.  If too many
customers switch on the AC, why don't these protect
the transformer from excessive current?

I lived on an Air Force base in the deep south for
many years.  Every year on the first really hot day of
summer, a large polemount (supported on a trestle
between two poles) transformer would fail at the
hottest part of the afternoon.  Even though this pole
unit was 2 or 3 blocks away, I could hear it fail just
before my base housing unit lost power.  I recall the
distinctive growling sound of power arcing so loud it
echoed around the base.  Once or twice I actually saw
the flicker of blue-white light playing off nearby
trees and structures, even in the brassy summer
sunshine.  Once it actually burst into a smokey,
spectacular fire, flaming oil dripping to the ground. 
Fortunately, the errant unit was in an open area away
from houses and streets.

This was between 1984-95, and I've forgotten exactly
how many times it failed, but it happened often enough
that I came to expect it every year--sort of like the
4th of July.  After one such summer failure, I noticed
the replacement unit was much bigger than before.  The
transformer never failed again.  I guess somebody
finally got a clue.

If the smaller, failure-prone unit was overloaded by
peak summer demand, why didn't the protective devices
kick in?



--- Tesla list <tesla@xxxxxxxxxx> wrote:

> ---------- Forwarded message ----------
> Date: Fri, 06 Jul 2007 17:59:39 +0000
> From: David Rieben <drieben@xxxxxxxxxxx>
> To: tesla@xxxxxxxxxx
> Cc: drieben@xxxxxxxxxxx
> Subject: Vegas pole pigs can't take the heat
> Hi all,
> Although this is not directly Tesla coil related, I
> thought that
> some of the collective knowledge of this list would
> be able
> to address this question, assuming that the
> moderator fore-
> bares to let this through. I noticed in the recent
> news that some
> of the pole transformers in Las Vegas were failing
> and catch-
> ing fire, supposedly due to the increased demand of
> running
> A/Cs. My question is that although 116*F is a bit
> warm, even
> by Las Vegas summer standards, Las Vegans (including
> their 
> local electrical utility) are certainly no strangers
> to triple digit
> summer temperatures and I would think that the A/Cs
> are go-
> ing to be running a plenty whether it's 116*F or
> "only" a more
> typical 105*F.? I can see where the entire power
> grid, as a
> whole, would be under additional strain due to above
> average 
> temperatures, but not the individual pole
> transformers, at least by 
> that much. We coilers talk all of time about how
> pole pigs are built 
> very robust and can easily handle 2 to 3 times their
> nameplate rating 
> for short duty cycles and can even be ran like 50%
> above their 
> nameplate rating continuously. It sounds to me like
> the said trans-
> formers in Las Vegas may have been a bit underrated
> to begin with and/
> or they may have been toward the end of, or even
> past their useful life 
> cycle and the current heat wave may have been the
> "straw that broke 
> the camel's back". Any more qualified comments?
> David Rieben

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