lutfulPremium
join:2005-06-16
Ottawa, ON Reviews:
 ·TekSavvy DSL
1 edit | next topic at request of nunya and dadawgs 3 pdf files ... from modern lightning research:
1. zap_rod: lightning surge does not follow deep grounding rod
2. zap_shelter: equipotential bonding fails miserably during strike
3. zap_tower: tower carries more current than grounding straps
Due to following comments made in previous discussion of ungrounded faraday cage:
said by nunya:Next topic: Chicken or the egg, which came first? Go My personal opinion only relates to "engineered" chicken ... assume chickens became extinct after crossing many dangerous roads and scientists recreated the maligned but tasty species by hatching a genetically modified pheasant egg.
said by DaDawgs:If there *ANYONE* here that actually understands lightening? Raise your hand or shut up... Fortunately for electrical engineers, physics of lightning is very simple compared to science behind evolution.
But scientists only started instrumented research of direct strikes in the past 20 years. I have personally studied a few hundred lightning and surge protection related research papers since 2003 from which I uploaded a handful with critical insight relevant to WISP installations.
Do we update well-established but inadequate methods ...
or do we suffer occasional lightning damage ...
and blame them on bad luck and poor "grounding"?
Sort of like the chicken-or-egg problem. |
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| is there no end?
at the request of snowpro
remember to take cover under the tree! |
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lutfulPremium
join:2005-06-16
Ottawa, ON Reviews:
·TekSavvy DSL
1 edit | Upoloaded best paper I got on personal safety ... when there is absolutely no alternative, you can assume the "lightning position" a few feet away from tree trunk. You may get a nasty shock but most probably you will survive. 
Why we need more "grounding" discussions in WISP forum ...
DaDawgs  lost $7000 worth of equipment and some ham suggested his ground rod needed to go even deeper.
Rhaas is installing expensive grounding/bonding system which may not actually prevent damage to equipment during next big lightning strike. |
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 davidgGood Bye My FriendPremium,MVM
join:2002-06-15
none | reply to lutful
there is NOTHING you can do to be 100% protected from a direct hit. i have seen sites with absolutely no grounding at all never get harmed by a direct hit, then again i have seen brand new R56 compliant sites have every board in the building blown apart.
proper grounding and bonding is done to bring everything to the same potential so it ALL acts together to direct and dissipate the voltage induced by nearby strikes and strikes to the tower itself. but a direct antenna/phone/powerline hit will cause damage to even the best protected sites. most strike damage at poorly done is caused by nearby strikes inducing voltage on lines. the equipment is not all at the same potential, and thus the voltage and current flows thru the paths of least resistance. think of the entire structure and everything in it as one big parallel circuit, current is going to flow thru it all.
as an example, in 1997 the county here put in a trunking system. everything was grounded/bonded per the installation instruction. but every time a storm rolled thru they took a hit that knocked out 50% or more of the stations. it turned out that 1 more ground wire was required to each station that was not included in the original instructions or site audit. once those additional ground wires were run, the county has not taken a single hit that damaged grounded equipment inside the shelter! they have had a couple AC units knocked out, but that because when the originals were worked on the HVAC techs disconnected the bonds and never connected them back.
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Lack of Preparation on YOUR Part does NOT Constitute an Emergency on Mine! |
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 DaDawgsPremium
join:2010-08-02
Deltaville, VA | reply to lutful
Actually the HAM told me to put in radials, I was the one who thought it might be better to go deeper because the customer's lawn would suffer if we put in radials.
I'm thinking that we should put in radials, additional 10' rods at the end of each radial and a couple of 20' rods in the center of the ground plane.
When you see pictures like the one of lightening striking the surface of water in the first pdf it brings home the idea that you simply can not sink those kinds of currents directly to a point ground.
29 kA strike? That's a lot of current. |
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| said by DaDawgs:I'm thinking that we should put in radials, additional 10' rods at the end of each radial and a couple of 20' rods in the center of the ground plane. Yes, and with that 4 thousand dollar grounding system you still have a 40/60 % chance of saving the $79 Ubiquity radio.
Customers need to understand that if they insist on leaving the network cable plugged in during thunderstorms then it is up to their insurance company to replace the computer.
I have all of my customers set up with wireless indoor LANs to eliminate my liability. The only thing wired to the outdoor unit is an $18 Wireless N newegg special. Even the most basic lightning protection is not cost effective for me to fool with.
Wake up and smell the new wireless pricing revolution ! |
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DaDawgsPremium
join:2010-08-02
Deltaville, VA
1 edit | said by 38632383:said by DaDawgs:I'm thinking that we should put in radials, additional 10' rods at the end of each radial and a couple of 20' rods in the center of the ground plane. Yes, and with that 4 thousand dollar grounding system you still have a 40/60 % chance of saving the $79 Ubiquity radio. Customers need to understand that if they insist on leaving the network cable plugged in during thunderstorms then it is up to their insurance company to replace the computer. I have all of my customers set up with wireless indoor LANs to eliminate my liability. The only thing wired to the outdoor unit is an $18 Wireless N newegg special. Even the most basic lightning protection is not cost effective for me to fool with. Wake up and smell the new wireless pricing revolution ! What you don't realize is that Ubiquiti does not produce a product that can do what my Canopy radios do. Another thing you don't realize is that when you have a pop with two or three hundred subs just being down a day or two can cost you as much as the hardware on the pop. So the situation may not be as simple as you see it to be...
The particular pop refrenced by Lutful was hit again last Thursday. Second weekend in a row that the service has been down in that 10 square mile service area...
$14,000.00 in damages so far in the past 14 days...
Ya think maybe it MIGHT be worth it to get a good ground on that pop?
I know Lutful to be an educated man with considerable expertise in this subject. He provides scientific documentation which (IF you can read it) is helpful to me in making the kinds of decisions that real engineers have to make. |
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WHT
join:2010-03-26
kudos:3 | said by DaDawgs:What you don't realize is that Ubiquiti does not produce a product that can do what my Canopy radios do. Not *yet* they don't.
Anyway...looking at that picture of a discharge on a golf course and into water, I'm going to have to say it is irrelevant to a WISP that has ground rods sunk into perpetually damp earth. There is no comparison. The lightning spread out under the grass because there was no easy route to any other place. |
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DaDawgsPremium
join:2010-08-02
Deltaville, VA
1 edit | reply to davidg
said by davidg:as an example, in 1997 the county here put in a trunking system. everything was grounded/bonded per the installation instruction. but every time a storm rolled thru they took a hit that knocked out 50% or more of the stations. it turned out that 1 more ground wire was required to each station that was not included in the original instructions or site audit. once those additional ground wires were run, the county has not taken a single hit that damaged grounded equipment inside the shelter! they have had a couple AC units knocked out, but that because when the originals were worked on the HVAC techs disconnected the bonds and never connected them back. Bolding added for contast... Then perhaps there was something additional that could be done to prevent strike damage after all.
I just care about the best way to protect my equipment.
We build things in such a way that we prevent damage as often as we are able. We live with the damage we could not prevent.
We don't stick our heads in the sand and pray. |
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DaDawgsPremium
join:2010-08-02
Deltaville, VA
1 edit | reply to WHT
said by WHT:said by DaDawgs:What you don't realize is that Ubiquiti does not produce a product that can do what my Canopy radios do. Not *yet* they don't. I'm not holding my breath. I know why they won't publish those receive bandpass curves.
said by WHT:Anyway...looking at that picture of a discharge on a golf course and into water, I'm going to have to say it is irrelevant to a WISP that has ground rods sunk into perpetually damp earth. There is no comparison. The lightning spread out under the grass because there was no easy route to any other place. Yeah, the man from north texas is talking about "perpetually damp earth". Tell that to the WISP in El Paso.
This is a GOLF COURSE where they water it every night to keep the greens green? Talk about your perpetually damp earth.
Now go back and reread the first linked PDF and try looking at the PICTURES.
All I care about are the facts, Lutful is posting facts.
You bring some facts to the table and you will be equally interesting. |
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davidgGood Bye My FriendPremium,MVM
join:2002-06-15
none | reply to DaDawgs
Re: next topic at request of nunya and dadawgs my point was that nothing is 100% guarantee, and that improper grounding is worse than nothing at all. the reason they got hit so easily was because they were IMPROPERLY grounded. they have not taken a hard direct antenna strike yet, but when they do there will be damage. yes you want to do all you can to direct lightning to limit damage, but you cannot prevent it completely.
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Lack of Preparation on YOUR Part does NOT Constitute an Emergency on Mine! |
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DaDawgsPremium
join:2010-08-02
Deltaville, VA | said by davidg:my point was that nothing is 100% guarantee, and that improper grounding is worse than nothing at all. the reason they got hit so easily was because they were IMPROPERLY grounded. they have not taken a hard direct antenna strike yet, but when they do there will be damage. yes you want to do all you can to direct lightning to limit damage, but you cannot prevent it completely. I agree completely and I have never seen anyone state that there was anything you could do to 100% guarantee there would be no damage, have you?
I can't imagine anyone saying they could give you a iron clad promise they could absorb 100% of lightening strikes without damage, can you? |
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DaDawgsPremium
join:2010-08-02
Deltaville, VA
1 edit | Re: next topic at request of nunya and dadawgs Alas it is August in North America and that means thunderstorms. There will be no vacations for the wicked.
I guess if we are going to talk about religious issues, it has long been my suspicion that I am struck by lightening more times in years when I have built up bad karma than in years when I have built up good karma.
I have no scientific justification for that. I can't quantify it but it jives with most of the silly stuff one sees in threads like this one.
"Alas, alas! Lightening is of the Gods! Therefore we can do nothing to save ourselves! We must submit to the Gods and stand naked in the field holding only the string of our kite and praying that we are not among the stricken."
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jcremin
join:2009-12-22
Siren, WI
kudos:2
1 edit | said by DaDawgs:Alas it is August in North America and that means thunderstorms. There will be no vacations for the wicked. I hear you.. Big storm just rolled through here about 2 hours ago... All towers look good, but About 40 customers (out of around 220) are offline. I know there are scattered power outages, but hopefully the rest followed the directions in the last email with instructions about how to unplug their equipment to save the cost of a service call and new router-boards (fingers crossed).
I see another storm nearing Minneapolis and headed this way in another 2-3 hours... Sleep is overrated (or so I try to tell myself) |
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 John GaltForward, MarchPremium
join:2004-09-30
Happy Camp
kudos:3 | . |
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lutfulPremium
join:2005-06-16
Ottawa, ON Reviews:
·TekSavvy DSL
| reply to davidg
said by davidg:proper grounding and bonding is done to bring everything to the same potential so it ALL acts together to direct and dissipate the voltage induced by nearby strikes I have been explaining why it is utterly impossible to "bring everything to same potential" during a lightning strike for 5 years now. Obviously I failed, but here goes again ... kilovolts potential difference would exist between the ends of a perfect ZERO ohm conductor because of its "self-inductance" ...
Please read at least the zap_shelter paper from Sandia Labs, even if you read only the text parts and conclusion. |
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lutfulPremium
join:2005-06-16
Ottawa, ON Reviews:
·TekSavvy DSL
| reply to DaDawgs
said by DaDawgs:When you see pictures like the one of lightening striking the surface of water in the first pdf it brings home the idea that you simply can not sink those kinds of currents directly to a point ground. 29 kA strike? That's a lot of current. Cellular tower researchers are measuring even 200kA+ direct strikes these days. BTW zap_tower and zap_shelter demonstrate nothing beats the very low inductance path provided through tower steel and concrete.
However any surface radials attached to top of a ground rod will improve its lightning surge performance. Fortunately this happens indirectly when multiple ground rods are bonded underground. |
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 superdogI Need A DrinkPremium,MVM
join:2001-07-13
Lebanon, PA
3 edits | reply to Anon
In case anyone hasn't noticed, we will all disagree with one another from time to time? In a public forum, it is best to use a calm non-insulting manner/tone when disagreeing with another members thoughts or ideas. I myself am guilty of getting caught up in the fray and using disconcerting remarks from time to time when I make a post. With that being said, a calm, professional adult conversation is the best way to handle a subject like this. Out of all the things we discuss in this forum, this has to be the most difficult one of all. IMHO, only the bible has more people with varying opinions when it comes to hot topics.
Lets all just try and keep it civilized, and perhaps we can actually get somewhere with this. We all stand a chance to learn something if we do.
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»www.wavecrazy.net
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