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Re: [TowerTalk] update: grounding questions: Ufer, strap, exothermic we

Subject: Re: [TowerTalk] update: grounding questions: Ufer, strap, exothermic welds
From: Jim Lux <>
Date: Mon, 18 Apr 2011 19:33:08 -0700
List-post: <">>
On 4/18/11 6:33 PM, Mat Eshpeter wrote:
> An update on this thread and a new question or two:
> Seems to be pretty well agreed that connecting the rebar to the tower and 
> radials is a good thing. The potential damage to concrete is attributed to 
> poor installation technique.
> I am confused about the preference for copper wire over strap for use as a 
> buried ground radial to interconnect ground rods, given the much lower 
> inductance of strap; it may be that the longevity of a big piece of buried 
> wire outweighs the lower inductance benefit of comparatively thinner buried 
> strap?

Strap isn't that much lower inductance than a round conductor.  It's
dominated by the length (1 uH/meter is a good round number).  What strap
buys you is the lowest AC resistance for a given amount of copper in a
single conductor (e.g. skin effect has a lesser effect on a strap).
(useful if you're doing something with higher HF frequencies where skin
depth gets pretty thin)

On the other hand, in high pulse current applications (e.g. lightning
grounding), you're typically more concerned about mechanical strength
because of the forces on the conductor.  And strap is harder to connect
to, etc.  All the standard fittings, clamps, exothermic welding
fixtures, etc. are all about round wires and rods.


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