[TowerTalk] Lightning Protection

[Michael Tope]

On 7/8/2013 12:17 PM, Jim Lux wrote:
> I think there's an enormous amount of almost correct info about
> grounding out there. Some of it dates from the days of running a
> single long wire against a ground rod. Some of it is from electrical
> codes (which have different objectives). Some of it is just plain
> misunderstanding of the physics, but has crept into the lore.
>
> (that sharp bends have much more inductance than gentle ones...
> provably wrong, but you see it in lots of places)

Yes, based on what I've heard others claim, I was under the impression 
that sharp bends had a lot more inductance, but it just occurred to me 
that right angle TEM transmission lines work reasonably well even 
without mitering (mitering or curving is better, but transmission lines 
still work without it).

If there was a really large increase in the inductance associated with a 
sharp right angle it doesn't seem like that would be true. I suppose 
sharp bends do concentrate the electric field to a greater degree than 
do smooth bends, so avoiding sharp bends might be relevant in an 
application where there is risk of arcing. Of course, I can imagine a 
lot of scenarios (depending on the exact geometry), where the end-to-end 
length of the ground conductor ends up being shorter if it is curved 
smoothly than it would be if it were bent sharply. In that case the 
inductance would be lower by virtue of the shorter conductor length.

Funny how domain specificity can block otherwise obvious insights.

73, Mike W4EF..................