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Re: [TowerTalk] re; exploding concrete

To: "Jim Lux" <>,"jeremy-ca" <>
Subject: Re: [TowerTalk] re; exploding concrete
From: "Gene Smar" <>
Date: Sat, 15 Sep 2007 21:10:58 -0400
List-post: <>
----- Original Message ----- 
From: "Jim Lux" <>
To: "jeremy-ca" <>
Cc: "David Gilbert" <>; "N7DF" <>; 
<>; <>
Sent: Saturday, September 15, 2007 8:16 PM
Subject: Re: [TowerTalk] re; exploding concrete

> Oh yeah, and the other thing that could lead to certain destruction
> would be if you coil the cable.  Run a current through a coil, and it
> tries to expand, and if the current is high enough, the forces will
> exceed the tension strength of the wire and it will come apart.  A
> transient current in a coil can also cause things in or near the coil to
> be squashed and deformed and destroyed.


     I was exposed to this phenomenon as an engineer with my local electric 
utility company years ago.  My group was responsible for purchasing and 
inspecting all the medium and large three-phase power transformers (5 MVA 
through 350 MVA+) that were installed at the substations around the system. 
These are the brutes that can be as large as a small house.  Besides 
insulation of the various windings (which was paper, BTW), the main thing I 
looked for when I inspected the transformers' cores before they were sealed 
inside the steel tanks was the bracing used to keep the phase windings in 
place under short-circuit currents.  ( For photos of the guts of a medium 
power transformer, see page 6 of .  For a 
view of the bottom of a transformer tank see page 7 ibid.)  As Jim said, 60+ 
kA of SS current could tear the windings apart as the magnetic fields in 
each phase repelled each other in the close space of the transformer tanks.

73 de Gene Smar  AD3F


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