[TowerTalk] More lightning stuff
K8RI-on-TowerTalk at tm.net
Mon Sep 15 23:10:44 EDT 2008
Jim Lux wrote:
> Ran across another interesting paper:
> http://www.lightningsafety.com/nlsi_lhm/Radials.pdf, a paper by Moore, et al, from the Langmuir Lab.
> Their recommendation is that radials for lightning dissipation should extend 8-10 meters from the down conductor. (based on height of stepped leader and the surface charge distribution)
> They also point out that a standard rod has sufficient inductance (2.4 uH, est) that it's not a particularly good lightning current sink, because it would still result in a radial electric field of several hundred kV/m. That field would result in radial streamers forming and propagating outward.
> The concern overall is that of "surface arcing"
Although not in the terms they use I think this is pretty much "common
knowledge" for most who have large systems and large ground systems.
For instance with just one tower that "towers" above everything else for
some distance, I have 32 or 33 8' ground rods cad welded to over 600' of
bare copper cable. Ours would not be a back yard in which to install a
swimming pool. Last time I guy dug back there with a back hoe I had to
have the basement wall fixed.<sigh>
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