[TowerTalk] Lightning... and pointed rods!

[David Robbins]

its just not possible to neutralize the charge between the ground and cloud that
way.  compare the currents measured on the downlead from one of those things to
the total charge of many coulombs built up between the cloud and ground.  also
the ions produced by the area of corona around those spikes travels way too slow
to ever get near the cloud.  the shielding effect of the cloud of ions would
also probably cover too small an area to be really useful and would be blown
away easily in a wind.  there are two reports that i know of that have studied
them in detail, both concluded that they didn't work as advertised.  i have also
read other articles from the international conference on lightning protection
that basically debunked them.

To quote John Anderson (consultant to where i work on lightning protection
design software) from a recent class we gave on lightning protection design for
transmission lines:

<quote>
Abdul M. Mousa, "The Applicability of Lightning Elimination Devices to
Substations and Power Lines," IEEE Transactions on Power Delivery, Vol. 13,
No. 4, Oct. 1998m pp. 1120-1127.

Paper was peer-reviewed by six reviewers under threat of lawsuits. Paper
states that these devices do not work as the manufacturers claim.

1997 Report on Dissipation Arrays, funded by FAA, Naval Research Labs, NASA,
and USAF

The report, 274 pp., compiled by 17 scientists and engineers from around the
world, provides no definitive physical or theoretical evidence that
lightning dissipation arrays prevent lightning. The USAF presented photos
showing the arrays being hit by lightning.
<unquote>

unfortunatly these spiney things have become a fad and have gathered many
supporters who claim they work.  but as stated other places most of the
improvement is probably due to simultaneous improvement in grounding or just
plain luck.  we have done other studies that show year to year variations of
10:1 or more in the numbers of strokes to the ground over fairly large areas. 
so it would not be surprising to have several strokes to a large building or
airport one year then nothing for the next several years... of course if you
installed hedgehogs after the first year they are credited with protecting you
the next couple years.

Bob Wanderer wrote:
> 
> Sorry, Norm, but the spline balls working that way (as they
> were originally touted) is just not true (please substitute
> a much stronger but politically incorrect term).  When I was
> at PolyPhaser, we used to provide a video from two TV
> stations and the FAA in Tampa proving the incorrectness of
> these beliefs.  The one from the FAA (just before the camera
> stopped running) clearly shows one of these "hedgehogs"
> being hit.  The FAA was interested in them (for obvious
> reasons) until the truth became obvious.  Then they were
> touted in another manner.
> 

-- 
David Robbins K1TTT
e-mail: mailto://k1ttt@berkshire.net
web: http://www.berkshire.net/~robbins/k1ttt.html or http://www.k1ttt.net
AR-Cluster node: 145.69MHz or telnet://k1ttt.net

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