On Oct 16, 12:13*pm, Jim Lux wrote:
Dave wrote:
A well grounded mast DOES NOT attract lightning any
better than a non grounded mast at the same location.

actually it does. *both the ieee and cigre have been using lightning
statistics data collected mostly from tall masts for many years.
There are well known formulas used to calculate the number of strokes
to a pole or power line, both include the height, and as height
increases so does the number of strokes to the object. *The height
also skews the current distribution with higher structures more likely
to get more high current strokes.

But, is there a difference in strike rate between grounded and
ungrounded towers of the same height. *I would think that the difference
would be very small, and smaller as the height gets bigger.

That's what I'm thinking. I know my well grounded mast is not a
lightning magnet. Some years I get no strikes to it. In fact, I think
it's been a few since the last one. Well, unless it was hit when I
was not at home.
I'm still of the opinion that the ability of an object to stream means
more than if it's grounded or not.
Airplanes are not grounded, and they get popped all the time.
Trees are poorly grounded, and they get popped all the time.
I've known quite a few people over the years that stuck a vertical
on their roof and didn't ground it, and they got popped. Blew
the ungrounded antenna to smithereens too..
Many golfers get popped on the golf course and they are not
really grounded too well unless they are wearing spikes on their
shoes. :/
I think the height of the object relative to it's surroundings, and
it's ability to stream mean more than anything.
Trees are a target lightning pick probably as much as anything,
and most are fairly poorly grounded due to being wood with some
moisture to helps things a bit. I think the trees ability to stream
well is why they get picked on so often. The pointy ends of a
leaf stream well, much like the pointy hairs on the head of a
golfer. And when you have hundreds of leaves on a tree...

But lets say a grounded mast does get struck slightly more than
an ungrounded mast. That would not a logical reason to avoid
grounding it, when the act of grounding the mast pretty much
negates the likelihood of a strike doing much damage to the mast
or the building next to, or under it.
A wooden mast would act much the same as a tree if it did not
have any kind of ground wire running along it's length.
That's why I never use wood masts here.
I'd rather have a grounded mast struck every 5 years with no damage,
vs an ungrounded mast struck every 10 years that led to heavy
damage or even burned the house down.
So worrying about that is kind of silly I think, when you know
an ungrounded mast is big trouble if it ever does get hit.