WXforum.net
General Weather/Earth Sciences Topics => Lightning => Topic started by: NHWF5510 on November 15, 2017, 03:18:09 PM
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Been searching the internet and having little luck getting a straight answer so i was hoping some members who have a good understanding of lightning can steer me in the right direction. I honestly don't really understand much about it.
I want to install a mounting pole for an anemometer. ideally 20-30' tall. The weather station would likely be mounted on it too. That being said, i don't want to "attract" lightning. Is a conductive pole a good thing? or a bad thing? Is a tall steel pole set in concrete going to attract lightning more than a steel pole bolted to a 6x6 wood post set in concrete? It's not realistic to go with a wood pole above 10' so that's not an option.
It's bad enough that a lightning strike could damage my weather station, but seeing as all my homes utility wiring is all underground as is my well pump wiring in the general vicinity of where i'm planning to put this pole i don't want to literally set myself up for a disaster.
We do get a good amount of lightning here and the previous homeowner already replaced a well pump once due to a strike.
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It's not so much an issue of "attraction", but what's going to happen if lightning hits.
A tall metal pole should be well-grounded. That way if lightning hits, it will be channeled safely to ground.
If it is not well-grounded (like your steel pole mounted in a wood post example), then the lightning is forced to pass through something of higher resistance (the wood). The wood will likely explode, if not burst into flame, from the current being forced through it.
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It's not so much an issue of "attraction", but what's going to happen if lightning hits.
A tall metal pole should be well-grounded. That way if lightning hits, it will be channeled safely to ground.
If it is not well-grounded (like your steel pole mounted in a wood post example), then the lightning is forced to pass through something of higher resistance (the wood). The wood will likely explode, if not burst into flame, from the current being forced through it.
Yea, but that would be cool.
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Ok, so i'm not making anything "safer" by mounting a steel pole to something wood. Good to know. Ill just set a steel pole in concrete and make sure the bottom is in direct contact with the earth. But my other question still remains,
Is having a well grounded steel pole on my front lawn going to attract a lightning strike more than say, the pine trees 50' away that are much taller? i'm just trying to find out if i am increasing the chances of getting a strike by doing this? Or will my giant trees surrounding my property still be more likely to be struck then a steel pole?
Again, the bottom line is i don't want to open myself up for major damage for the sake of my weather station by doing this the wrong way.
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Ok, so i'm not making anything "safer" by mounting a steel pole to something wood. Good to know. Ill just set a steel pole in concrete and make sure the bottom is in direct contact with the earth. But my other question still remains,
Is having a well grounded steel pole on my front lawn going to attract a lightning strike more than say, the pine trees 50' away that are much taller? i'm just trying to find out if i am increasing the chances of getting a strike by doing this? Or will my giant trees surrounding my property still be more likely to be struck then a steel pole?
Again, the bottom line is i don't want to open myself up for major damage for the sake of my weather station by doing this the wrong way.
Lightning often hits taller objects first. It depends on how close they are and how much taller they are. The further away they are, the less "protection" they provide.
That's not 100% a sure thing, though. For example, lightning will sometimes strike the side of a tall building or tower instead of the top.
It's just very hard to predict exactly what lightning will do. That's why it's best to prepare by assuming it WILL eventually hit, and providing it a safe path to ground.
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Ok, so i'm not making anything "safer" by mounting a steel pole to something wood. Good to know. Ill just set a steel pole in concrete and make sure the bottom is in direct contact with the earth.
My $0.02 is to drive a ground stake per NEC recommendations as a minimum. Personally, I would Google the recommendations for amateur/ham radio operator towers and do that. Just being in contact with the ground does not guarantee that the sudden discharge will be properly dissipated.
Something to think about. The lightning bolt jumped a 5-mile-long arc between the ground and cloud. Why does anyone think that a half inch of rubber or 6-foot wooden fence post is going to stop it?????
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Lightning always takes the path of least resistance to dissipate its charge. I have investigated fires where lightning has done some amazing things. With that being said, a lightning rod or pole grounding is an attempt to divert the strike safely away from what it is mounted on. Given the power of a lightning bolt though, the lightning rod and associated wires or straps are likely to be reduced to molten material and will be distributed around the area of the strike. The only thing I have seen survive is a 1200 ft commercial radio tower because it can deal with the current dissipation and had massive distribution points on the base that ran all the way to bedrock. I would go so far as to say that a lightning rod is a feel good effort.
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Lightning always takes the path of least resistance to dissipate its charge. I have investigated fires where lightning has done some amazing things. With that being said, a lightning rod or pole grounding is an attempt to divert the strike safely away from what it is mounted on. Given the power of a lightning bolt though, the lightning rod and associated wires or straps are likely to be reduced to molten material and will be distributed around the area of the strike. The only thing I have seen survive is a 1200 ft commercial radio tower because it can deal with the current dissipation and had massive distribution points on the base that ran all the way to bedrock. I would go so far as to say that a lightning rod is a feel good effort.
I have to strongly disagree. I've seen the effects of lightning striking my parent's house both with and without lightning protection. I came face to face with ball lightning inside the house with the unprotected strike.
Lighting rods do their job if properly installed.
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Depends on whether or not it is a feeder branch or direct hit.
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Depends on whether or not it is a feeder branch or direct hit.
Duh... they were direct hits, though.
Saying lightning rods are a "feel good effort" is just insane and irresponsible.
I've seen the results of lightning strikes on all sorts of things as an electrical engineer. Properly installed, the lightning rods and associated cables don't vaporize.
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We will have to agree to disagree! I had pictures and documentation, you have anecdotes. There is no reason for you to be sarcastic and condescending.
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We will have to agree to disagree! I had pictures and documentation, you have anecdotes. There is no reason for you to be sarcastic and condescending.
I've got way more than anecdotes, bud. You're the one calling an entire industry "feel good".
Again, lighting protection works. Otherwise engineers wouldn't be spending all the money protecting structures and equipment.
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Maybe the question should be will an individual have the knowledge, take the time and spend to money to properly ground a pole for their weather station?
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Maybe the question should be will an individual have the knowledge, take the time and spend to money to properly ground a pole for their weather station?
As mentioned before, there are published standards for things such as TV and amateur radio antennas, which have been found to work well.
It's not terribly hard or expensive. Good sense might be in short supply, though. The biggest problem I see is that ground rods are often not what they should be. I've seen some installations where folks have grounded to a water supply pipe outside their house, not realizing the connection to the water main isn't metal (!). Or they don't sink a copper ground rod deep enough in dry stony soil that isn't terribly terribly conductive.
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Straight from the ARRL (National Assoc for Amature Radio) it says http://www.arrl.org/files/file/Technology/tis/info/pdf/0208053.pdf :
The primary purpose of the external ground system is to
disperse as much of the lightning energy as possible into the
earth before it follows the feed line into the radio station. No
matter how hard one tries, some of it will follow the coax,
which is why you created the protection plan for the radio
equipment. The easier you make it for the strike energy to
dissipate in the earth before it gets to the radio station, the
less your equipment protection plan will be stressed.
With great diligence, hard work, no real estate restrictions,
plenty of funds and highly conductive soil, it is possible for up
to 90% of the strike energy to be dissipated in the earth, leaving
just 10% heading for your equipment.
Radials and Ground Rods
Spreading out from the base of the tower is a set of eight
radials. While the number of radials required for a particular
installation will be dependent on the soil conditions in your
location, the system shown here is a reasonable start. Each
radial is a bare copper wire (preferably, strap) buried 6 to 18
inches below grade. The radials should be positioned so that
the energy is dissipated away from the house.
Connected to the radials are ground rods. The ground rods
are spaced approximately twice the length of a ground rod.
For an 8-foot rod, the spacing would be 16 feet.
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Doesn't sound easy or cheap to me :)
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Doesn't sound easy or cheap to me :)
Not if you're also adding in radials for antenna performance.
He's mixing two different applications.
The NEC codes for grounding antenna masts are nothing like this.
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Well, you are the one that said look for standards for amateur radio antennas,
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Well, you are the one that said look for standards for amateur radio antennas,
Yes. For grounding masts.
And I wasn't the first to bring up the subject.
Sheesh...
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While a strike can go through a plane, for instance, with minimal or even no damage, and the space shuttle during launch, and tall buildings and heavily grounded towers may not be hit often, I'm wondering if a very well grounded tower will dissipate the charge building up, and actually thwart a strike from happening?
I've spent many storms watching a 1000' tower here with lightning dancing all around expecting that the easy path to ground through the tower would make it very likely to be hit. Despite all the watching, never a strike seen, although some of the old old radio guys here in town and the engineers say it does get hit once in awhile.
So a properly grounded tower, big or small, might be draining away the charge and keeping a strike from occurring, or am I wrong on that one?
And I recall some antennas on mobile radios we used to install had a little round BB or bigger sized thing crimped on the end of the wire to cut down on noise, and the explanation was that the round surface dissipated any build up from travel through the air (rubbing cat syndrome, St. Elmo's fire in planes) and that sharp edges like a square cut across the wire makes it more likely to have radio noise.
Just curious about these two things.
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While a strike can go through a plane, for instance, with minimal or even no damage, and the space shuttle during launch, and tall buildings and heavily grounded towers may not be hit often, I'm wondering if a very well grounded tower will dissipate the charge building up, and actually thwart a strike from happening?
I've spent many storms watching a 1000' tower here with lightning dancing all around expecting that the easy path to ground through the tower would make it very likely to be hit. Despite all the watching, never a strike seen, although some of the old old radio guys here in town and the engineers say it does get hit once in awhile.
So a properly grounded tower, big or small, might be draining away the charge and keeping a strike from occurring, or am I wrong on that one?
And I recall some antennas on mobile radios we used to install had a little round BB or bigger sized thing crimped on the end of the wire to cut down on noise, and the explanation was that the round surface dissipated any build up from travel through the air (rubbing cat syndrome, St. Elmo's fire in planes) and that sharp edges like a square cut across the wire makes it more likely to have radio noise.
Just curious about these two things.
The first one is an age-old debate. Stormhighway talks about it here: http://stormhighway.com/lightning_rods_discharge_thunderstorm_cloud_myth.php
I'm not familiar with the 2nd one.
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Thank you all for the information. Some good info being posted here. I still have not really received a clear answer though as to my primary question. Simply put, is adding a properly grounded steel pole going to INCREASE my chances of taking a direct hit even if it's not as tall as adjacent trees? Or will it make no difference at all?
As for lightning rods, working as both a firefighter and for the railroad i have seen the effects what lightning can do. To say that lightning rods are a "feel good" is completely false. I have been to quite a few house and building fires caused by lightning strikes. I remember a multi family home that took a direct hit to the main sewer vent stack for the house. it melted all the lead joints and set fires in all the walls the pipe passed through. The electric panel was blown completely off the wall and we found pieces of it on the other side of the room. But none were on structures with lightning rod systems.
Lightning has wreaked havoc on the railroad between Boston and NYC where i work. But each time repairs were made and they spent the money for lightning protection the problems never returned. We had one location that used to get hit more than once a year. They finally spent the $$ to properly protect it and it's been fine ever since.
Done right, lightning protection systems are absolutely a worthwhile investment. Certainly not a guarantee of never having damage, but far better than no system at all.
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The grounding is for "safety", to drain the static buildup into the ground, and should help to not attract lightning as opposed to not grounding a pole and the wind blowing over it and static electrically charging it up. There is never any guarantee that lightning will not hit a pole, but you want to take appropriate measures to be sure that if it does, you take as much of the power of it to the ground outside, and not through your home wiring system to get it into the ground, which is where it is trying to get to in the first place. Lots of damage and fire can occur without a proper ground.
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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.
Sent from my iPhone using Tapatalk
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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.
Sent from my iPhone using Tapatalk
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?
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The grounding is for "safety", to drain the static buildup into the ground, and should help to not attract lightning as opposed to not grounding a pole and the wind blowing over it and static electrically charging it up. There is never any guarantee that lightning will not hit a pole, but you want to take appropriate measures to be sure that if it does, you take as much of the power of it to the ground outside, and not through your home wiring system to get it into the ground, which is where it is trying to get to in the first place. Lots of damage and fire can occur without a proper ground.
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.
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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.
Sent from my iPhone using Tapatalk
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.
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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
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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.
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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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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.
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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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http://today.tamu.edu/2012/02/29/lighting-rods-work-says-expert/
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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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AMS Statement on Lightning Protection Systems
https://www.ametsoc.org/ams/index.cfm/about-ams/ams-statements/archive-statements-of-the-ams/lightning-protection-systems/
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You might be interested in these. Fiberglass poles.
http://www.tmastco.com/main/page_products_telescopic_poles.html
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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
Well of course I would listen to a storm chaser / photographer over a degree holding engineer.
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http://today.tamu.edu/2012/02/29/lighting-rods-work-says-expert/
Of course the systems are grounded for when lightning does strike.
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Well of course I would listen to a storm chaser / photographer over a degree holding engineer.
Well, gee. I guess you've got one here, then.
Or do you want to listen to a crackpot who thinks lighting rods are just "feel good" measures.
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http://today.tamu.edu/2012/02/29/lighting-rods-work-says-expert/
Of course the systems are grounded for when lightning does strike.
It appears you aren't following along.
And your point is what, exactly?
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Well of course I would listen to a storm chaser / photographer over a degree holding engineer.
Well, gee. I guess you've got one here, then.
Or do you want to listen to a crackpot who thinks lighting rods are just "feel good" measures.
I never said they were a "feel good" measure.
This is getting quite boring.
You remind me of a certain American politician who can't tolerate someone with another opinion.
I'd bet you're a supporter.
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Well of course I would listen to a storm chaser / photographer over a degree holding engineer.
Well, gee. I guess you've got one here, then.
Or do you want to listen to a crackpot who thinks lighting rods are just "feel good" measures.
I never said they were a "feel good" measure.
This is getting quite boring.
You remind me of a certain American politician who can't tolerate someone with another opinion.
I'd bet you're a supporter.
Which just goes to show you haven't been following the thread at all.
Maybe you should read before you comment.
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How would you protect this? Someone told me that the lightning arrester or two is enough and there's no need to ground it.
(http://www.imagehosting.cz/thumbs/dehaqpgxka.jpg) (http://www.imagehosting.cz/?v=dehaqpgxka.jpg)
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How would you protect this? Someone told me that the lightning arrester or two is enough and there's no need to ground it.
(http://www.imagehosting.cz/thumbs/dehaqpgxka.jpg) (http://www.imagehosting.cz/?v=dehaqpgxka.jpg)
There needs to be a good ground to provide a safe path for the current flow should lightning strike, lighting arrester or not.
Otherwise, the current will probably pass through the brick, causing any moisture in the brickwork to flash into steam and explode.
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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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On the farm, we have that on the barn, corn crib, old garage and house/tv antenna.
Amazingly, when mom and dad had a CB radio antenna, I don't remember it being grounded. I took it off the roof when we moved. When it stormed, we unhooked it from the CB and put the cord in a glass jar.
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How would you protect this? Someone told me that the lightning arrester or two is enough and there's no need to ground it.
(http://www.imagehosting.cz/thumbs/dehaqpgxka.jpg) (http://www.imagehosting.cz/?v=dehaqpgxka.jpg)
Is that a transmit antenna?
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When it stormed, we unhooked it from the CB and put the cord in a glass jar.
So you could catch the lightning bolts and sell them?
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How would you protect this? Someone told me that the lightning arrester or two is enough and there's no need to ground it.
Is that a transmit antenna?
Nope, I use it generally for VHF monitoring and reception of APT/LRPT (weather satellites)
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How would you protect this? Someone told me that the lightning arrester or two is enough and there's no need to ground it.
There needs to be a good ground to provide a safe path for the current flow should lightning strike, lighting arrester or not.
Otherwise, the current will probably pass through the brick, causing any moisture in the brickwork to flash into steam and explode.
Thanks for advice, I'll do that.
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When it stormed, we unhooked it from the CB and put the cord in a glass jar.
So you could catch the lightning bolts and sell them?
Yup. Stupid idea. Can't figure out why the seller told us to do that. The only thing it would do would stop the base from getting fried.
Unlike the night the phone blew off the wall from lightning hitting the line a mile away.
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When it stormed, we unhooked it from the CB and put the cord in a glass jar.
So you could catch the lightning bolts and sell them?
I "think" that is how he paid for college, selling them to those along with various body gases.
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I wish!
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I wish!
You know what I wish ? I wish I had Miralax and Linzess back when I was in college. There are a few football players that I would have dosed their beer with that stuff on a regular basis. Seemed they were so shitty anyway, would make noise when we had to study, turned up their radios to max when we complained. Yup Linzess and Miralax.. Might even could have inproved their sprinting times.