Author Topic: Mounting poles and NOT attracting lightning.  (Read 915 times)

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Offline ocala

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Re: Mounting poles and NOT attracting lightning.
« Reply #25 on: November 22, 2017, 03:40:55 PM »
Static charge on the mast is irrelevant in this case.

Grounding the mast doesn’t make it any more attractive to lightning.  It would just as likely strike the mast if it were ungrounded.

The difference is the grounded mast would provide a safe path to ground, limiting any damage.  An ungrounded mast, like one separated from ground by wood as you originally suggested, would cause damage as the lightning tries to pass through the wood.


In short, lightning doesn’t “know” how well something is grounded before it hits. 


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  This is interesting. And leads me to another relevant question on the subject of masts and lighting.

 Many people opt to mount their anemometers on the roof. This can be done via a chimney mount, tripod mount or an eave mount. Whatever the mount, these typically support a metal pole and are completely un-grounded. Usually bolted into wood or masonry. But this will almost always mean it's the highest point on the roof as well. Do these become more of a target for lightning? Or are they "invisible" to lightning because they offer no easy path to ground?
I have had my anny mounted on my antenna tower since 04. Only 1 strike in that time but it destroyed everything. It was a cabled unit. Living in Florida we get some serious lightning in the summer so 1 strike in 13 years isn't too bad.

Offline nincehelser

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Re: Mounting poles and NOT attracting lightning.
« Reply #26 on: November 22, 2017, 04:00:00 PM »

I agree
i used to manage data centers and all my buildings had lightning protection systems on the roof.

I have been told several times by the companies that install and maintain these systems that their main purpose is to dissipate the static charge that develops under a large cloud.
thus reducing the potential for a strike.

That's a myth. 

http://stormhighway.com/lightning_rods_discharge_thunderstorm_cloud_myth.php

Offline Phil23

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Re: Mounting poles and NOT attracting lightning.
« Reply #27 on: November 22, 2017, 04:18:39 PM »
Interesting,

Got me thinking of the old TV tower in my parents yard.

The old triangular type seen during the 60's,
about 1m at the base & guessing 20m high, as it laid diagonally across the back yard when it was lowered.

When it was standing it had another 5m tube that extended & was guy wired at the top,
so probably 25m in total height.

Don't think I have any recollection of it ever being struck in the past 50+ years.

That was in the era when the closest TV transmitters were 200-300km away.

Phil.

Offline eyecue

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Re: Mounting poles and NOT attracting lightning.
« Reply #28 on: Yesterday at 08:46:48 PM »
There are 4 types of lightning; cloud to cloud, cloud to ground, ground to cloud and ball.   A lightning rod will attempt to dissipate the ground to cloud strike by allowing the static charge to dissipate into the air if the air is more positively charged.  It will have no effect if the lightning targets the object the rod is mounted on if the lightning is cloud to ground.  A ground wire of the standard size used for residential wiring (#6 or #8 AWG) will not be able to deal with the amperage from cloud to ground (20,000 Amps)  it also cannot deal with the temperature that is 5 times the surface of the sun.  Lightning cannot be stopped or controlled, it is random and subject to a lot of speculation.  I have treated people hit by it and investigated fires started by it. Having a lightning rod is like wearing a necklace that the seller says stops  orange polar bears from attacking.  When questioned about orange polar bears being non existent, the seller says "see how good it works!" If cloud to ground targets something taking the path of least resistance, there is nothing to do but watch what happens.
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Offline nincehelser

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Re: Mounting poles and NOT attracting lightning.
« Reply #29 on: Yesterday at 08:53:58 PM »
There are 4 types of lightning; cloud to cloud, cloud to ground, ground to cloud and ball.   A lightning rod will attempt to dissipate the ground to cloud strike by allowing the static charge to dissipate into the air if the air is more positively charged.  It will have no effect if the lightning targets the object the rod is mounted on if the lightning is cloud to ground.  A ground wire of the standard size used for residential wiring (#6 or #8 AWG) will not be able to deal with the amperage from cloud to ground (20,000 Amps)  it also cannot deal with the temperature that is 5 times the surface of the sun.  Lightning cannot be stopped or controlled, it is random and subject to a lot of speculation.  I have treated people hit by it and investigated fires started by it. Having a lightning rod is like wearing a necklace that the seller says stops  orange polar bears from attacking.  When questioned about orange polar bears being non existent, the seller says "see how good it works!" If cloud to ground targets something taking the path of least resistance, there is nothing to do but watch what happens.

More BS.

Lightning rods are well proven effective in preventing damage from lightning strikes.

They don’t prevent lightening strikes (nor do they cause them), but they do shunt the current safely to ground.  They don't "vaporize", either.

You are simply wrong.

You might want to learn how lighting rods are installed and used.  You don't ground lightning rods with standard house wiring.


« Last Edit: Yesterday at 09:01:11 PM by nincehelser »

Offline DaleReid

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Re: Mounting poles and NOT attracting lightning.
« Reply #30 on: Yesterday at 09:06:05 PM »
I've seen braided wire used to bond lighting rods, and there are installation guidelines to avoid tight bends, etc, which I assume increases the inductance.

While these cannot carry a 1/4 million amps for very long, I'm thinking either the pulse is too short to do much damage, or that the ionization around it during the pulse allows current to flow through that

You always see how a tree explodes, or some other dramatic damage occurs with some strikes.  This is the water in sap or wood boiling and is like a hot piece of metal dropped into a quenching bath and a violent boil occurs.

In another life I was interested in the microsecond events that occur when a fission weapon goes off.  The expansion of the fireball from zero radius to the first few hundred feet goes through several different stages, with various degrees of opacity of the surrounding air and while one might think what goes on is defying logic, those with access to the data from such events can explain why it does what it does. 

I'm all for finding out as much about nature as I can and want to know facts, as best they are understood by experts, rather than wave my hands and say there is some magical mysterious event going on.  The problem with lightning it is hard to reproduce as it naturally occurs, and the calculations to determine air conductivity and resistance with micro scale humidity and particulate matter and many other factors make coming up with a reasonable model very hard.

Fortunately fewer people smoke nowadays, but if there is a very still room and someone has a cigarette burning, watch the smoke rising.  The first few inches off the cigarette the smoke comes up relatively straight, but then it begins to weave back and forth and even fold on itself and split apart.  The modeling of that air flow is hard.  Sort of the same thing with lightning, I'd bet.
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Offline nincehelser

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Re: Mounting poles and NOT attracting lightning.
« Reply #32 on: Yesterday at 09:24:46 PM »
Here's an example of the kind of cable that ties lightning rods together and to the ground on most home installations I've seen.

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