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shielder
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best practice for lightning protection

Sun Jun 14, 2009 10:14 am

Hi all,

I believe most of us have encounter lightning strike problem. So let us share our experience for the best practice to avoid lightning problems.

Best regards,
Budiarto
 
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Re: best practice for lightning protection

Sun Jun 14, 2009 2:56 pm

No problems here. I use a floating ground system on lightning-exposed units. No connection to any ground anywhere. No surge/lightning suppressors on my antennas. My most exposed unit is on top of a 22 story building next to one of the busiest lightning rods on the roof. It just celebrated its first anniversary there this week with no incident at all.

If you think maybe it is just my location, think again. "Lightning Capital of the World"
 
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Re: best practice for lightning protection

Sun Jun 14, 2009 4:47 pm

I call that lucky Tim,

There are ground paths through your ethernet and power supply.

Or are you running fiber on the ethernet and an isolation transformer for the power?

Tom

10 years of radio and lightning experience and I have tried it all.
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Re: best practice for lightning protection

Sun Jun 14, 2009 4:56 pm

I call that lucky Tim,

There are ground paths through your ethernet and power supply.

Or are you running fiber on the ethernet and an isolation transformer for the power?

Tom

10 years of radio and lightning experience and I have tried it all.
No luck. Strictly science. If you are in your car, and a power line falls across it in a storm, what is the recommended course of action? DO NOT GET OUT! Do not complete any circuit to ground with your foot. The tires will insulate you. Rubber and air. Great insulators.

I use solar power/batteries for these applications, and all radio for internet connection. No connection to any ground at all. Good thing! One of those boxes I bought from you!
 
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Re: best practice for lightning protection

Sun Jun 14, 2009 5:33 pm

I call that lucky Tim,

There are ground paths through your ethernet and power supply.

Or are you running fiber on the ethernet and an isolation transformer for the power?

Tom

10 years of radio and lightning experience and I have tried it all.
No luck. Strictly science. If you are in your car, and a power line falls across it in a storm, what is the recommended course of action? DO NOT GET OUT! Do not complete any circuit to ground with your foot. The tires will insulate you. Rubber and air. Great insulators.

I use solar power/batteries for these applications, and all radio for internet connection. No connection to any ground at all. Good thing! One of those boxes I bought from you!
so no grounding whatsoever? do you insulate your antennas using rubber or something? Last year I had a lot of issues with surge's via lightning, went right through the ethernet cable to the RB and wireless card all went dead. But considering your using solar and air, No surges Nice :-) -Jordan B
~Agricultural WISP "ZONE"~ Beware of oncoming cattle and dont hit the farmer!!! I need to ask him about using his silo for an AP first"~

*Automated Billing Installer* http://wiki.mikrotik.com/wiki/AutomatedBilling Built by Krige ;-)
 
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Re: best practice for lightning protection

Sun Jun 14, 2009 5:50 pm

Nothing. Nada. Like the Knights Who Say "Nicht"! (Monty Python and the Holy Grail) Here is a pic of "Mom". She runs my show at this location. Flawless!
http://www.wififoryou.com/lightning.jpg
The red circle is the lightning rod. It has been hit so many times, the screws have been blown out of the railing, and the tip is bent and discolored.

ADD: Bring me a.....SHRUBBERY! Not too big...
 
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Re: best practice for lightning protection

Sun Jun 14, 2009 6:55 pm

No luck. Strictly science. If you are in your car, and a power line falls across it in a storm, what is the recommended course of action? DO NOT GET OUT! Do not complete any circuit to ground with your foot. The tires will insulate you. Rubber and air. Great insulators.
In a car there the insulation isn't made by the tires, but with "Faraday Cage" rules.

See here:

http://en.wikipedia.org/wiki/Faraday_cage

I think you are a lucky guy =) .
 
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Re: best practice for lightning protection

Sun Jun 14, 2009 7:11 pm

Faraday cage is part of the equation, but not all of it. That is what protects the individual components from damage, but only because there is no ground path. Call it lucky...

ADD: I disagree on the insulation. The tires are the major insulation in this scenario.
 
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Re: best practice for lightning protection

Sun Jun 14, 2009 10:18 pm

Direct strikes arre not so common, and if equipment gets direct hit, there i sno point of protection.

What matters is protecting from unducted high voltage that shows up during the ligtning. That is what usually damages equipment.

The best way I found out is using antennas that do not produce inducted high voltage - waveguides of all kinds, for an example. Antennas that are built on wires (like colinear, or dipoles of all kinfs) are highly risky.

Also cables including UTP should be shielded and grounded to lead inducted voltage to the ground before it become dangerous for electronics.
 
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Re: best practice for lightning protection

Mon Jun 15, 2009 12:59 pm

Just a question...how many people have been driving in a car and the car was hit by lightning? Or the car in front of you? Or next to you? Or going the other way? I guess it is because nobody has the nerve to drive in a storm! :wink:
 
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Re: best practice for lightning protection

Mon Jun 15, 2009 1:36 pm

Just a question...how many people have been driving in a car and the car was hit by lightning? Or the car in front of you? Or next to you? Or going the other way? I guess it is because nobody has the nerve to drive in a storm! :wink:
http://www.youtube.com/watch?v=RvG3ieOh8cI

http://www.youtube.com/watch?v=vQ0_Lwa4 ... re=related
 
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Re: best practice for lightning protection

Mon Jun 15, 2009 2:03 pm

Just a question...how many people have been driving in a car and the car was hit by lightning? Or the car in front of you? Or next to you? Or going the other way? I guess it is because nobody has the nerve to drive in a storm! :wink:
http://www.youtube.com/watch?v=RvG3ieOh8cI

http://www.youtube.com/watch?v=vQ0_Lwa4 ... re=related
The first video: The damage was "Oh my God!", and replaced the antenna. The car stopped because of the flat tire. My question is; Did the lighning blow out the tire? Or did they have a flat, lowering the resistance to ground, and then get hit?
As far as I see, the second strike (hard to tell what car it hit) apparently didn't even take out the car's lights. It was still driving. Is there any more of that video or pics that shows what happened to the car?
 
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Re: best practice for lightning protection

Mon Jun 15, 2009 2:08 pm

By the way car is the safest place where you can be during the storm.
 
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Re: best practice for lightning protection

Mon Jun 15, 2009 6:04 pm

I'm going on to this direction on a hill top install:

- Hardware isolated from ground using a fiberglass pole (windsurf mast :D)
- Lightning rod close to it, but a different mast;
- Data over a small media converter + mono mode fiber;
- Powering via 14Ah sealed lead-acid battery + solar pannel. Durying working hours run an automatic charger from 220V that is connected - or not - to AC via an huge relay close to it (the charger is at the same battery cabinet). A second relay is at the begin of such 220V wires (250m away where mains is avialable). When I cut AC at the office all 250m is floating, both ends.

I saw once on the web a design that used a VLF AM receiver (small size, like a portable AM radio) with a ferrite rod anntenna (around 70 ... 200 KHz) where you can set some trigger point based on bg noise level. As soon as some lightning storm aproaches (may be far away) this circuit activate a relay etc. Seems ok, except if the vy first strike is at your own instalation ... :D

Regards;
Marcus Ramos
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(Microwave HW, RF, antennas, propagation)
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Re: best practice for lightning protection

Tue Jun 16, 2009 6:10 am

http://www.youtube.com/watch?v=ve6XGKZxYxA -- another good one from our friends at top gear :-)
 
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Re: best practice for lightning protection

Tue Jun 16, 2009 7:58 am

I call that lucky Tim,

There are ground paths through your ethernet and power supply.

Or are you running fiber on the ethernet and an isolation transformer for the power?

Tom

10 years of radio and lightning experience and I have tried it all.


I don't think tires will insulate you at all... first, tires and road and car metal parts are all soak wet so there practically is no insulation, also the lightning electricity has already travel thousands of meters, how in the world will 7 - 20 cm. of wet rubber act as an insulator... that's a non-sense ... is the faraday cage effect what's rule there...

If the equipment is connected via RF and batteries and solar power, and floating ground and whatever you may suggest... once in a lightning strike path it will kiss moma good bye anyway no matter what...
 
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Re: best practice for lightning protection

Tue Jun 16, 2009 9:56 am

I call that lucky Tim,

There are ground paths through your ethernet and power supply.

Or are you running fiber on the ethernet and an isolation transformer for the power?

Tom

10 years of radio and lightning experience and I have tried it all.


I don't think tires will insulate you at all... first, tires and road and car metal parts are all soak wet so there practically is no insulation, also the lightning electricity has already travel thousands of meters, how in the world will 7 - 20 cm. of wet rubber act as an insulator... that's a non-sense ... is the faraday cage effect what's rule there...

If the equipment is connected via RF and batteries and solar power, and floating ground and whatever you may suggest... once in a lightning strike path it will kiss moma good bye anyway no matter what...
Good theory! So, how many cars have you seen hit by lightning? 10? 20? 100? Gotta be a lot if that is true. I have yet to see even one in my 40+ years of driving. The Faraday cage effect will NOT prevent a lightning strike! Only protects the internals from damage. The electricity would still be conducted to ground around the cage.

EDIT: omega-00: Nice demo on the video. That is a keeper! But that was not really lightning. That was a Tesla Coil with the center of the car directly in line with the electrical path. Absolutely spendid demonstration of a Faraday cage. How does it do if the car is moved from under the anode just a little? Does the car still attract the electrical current if there is nothing between the anode and ground? If the test is valid, it should attract the current up to about thirty degree angle before breaking off.

EDIT2: Now lets make him like one of your radios (not mine. They are like he was in the test). Let's put a ground wire in his mouth. Now start the coil!
Last edited by SurferTim on Tue Jun 16, 2009 4:37 pm, edited 2 times in total.
 
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Re: best practice for lightning protection

Tue Jun 16, 2009 11:22 am

as far as i know energy build-up starts on both sides - from ground and from clouds - when the ends meet we see discharge, so, tires are good insulator to avoid that build-up of polarisation in the first place.

Also - rain water contains almost no salts in it - pure water is insulator, and salts(oxides) in the water only makes water conductive, because then water can be ionised.

Search in the wireless section - there is good article with pictures how to protect your equipment from lightning strikes and weird static charge build-up in antenna, that will blow our wifi card.
 
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Re: best practice for lightning protection

Tue Jun 16, 2009 9:13 pm

http://www.youtube.com/watch?v=ve6XGKZxYxA -- another good one from our friends at top gear :-)
If you are interested in this topic, you need to see this video!! In theory, this is what I am using. I mentioned this video in an earlier post, but now feel it is so relevant, I want to draw special attention to it. Like I said before, the Faraday cage effect does not prevent a lightning strike, but it does protect the internals. Even the FM stereo was undamaged. The results would be drastically different if he had a ground wire between his teeth.
Thanks, omega-00!

However, it does not prove to me one way or the other why cars are almost never hit by lightning. The only reason I can deduce is the tires. And if the car in the following video had a flat just before it was hit by lightning, as the end of the video may indicate, that would sway me even more towards the tire phenomenon.
http://www.youtube.com/watch?v=RvG3ieOh8cI
 
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Re: best practice for lightning protection

Tue Jun 16, 2009 10:51 pm

The tires.... huh?

-- The water on the tires is not conductive because is clean !!!! K'mon are the tires sterilized or what? --- Nah I don't think so....

Check this video clip: http://www.youtube.com/watch?v=eX6Xk0DRVvE



Check the distance between the airplane and the ground and compare it to the "sterilized wet tires" distance from the rim to the floor.... as I mentioned if you are in the lightning strike path what ever gear is grounded or near ground will kiss moma good bye..... no matter what. In the plane scenario like the car the current flows on the exterior surface only and continues it path to ground.

Actually (What I have read) the lightning electrical charges goes FROM ground TO cloud, the current flow is ALWAYS from the negative to the positive unless Kirchhoff is wrong : http://en.wikipedia.org/wiki/Kirchhoff's_circuit_laws , the light or flash we see goes from the cloud to the ground because the energy liberation starts from the contact point (cloud).

On the other hand, of course the Faraday cage IS NOT to avoid lightning is of course, to provide a path to ground, but remember simple basic electricity, V=I*R that is I=V/R so if you are talking about a resistance to ground of just 0.1 ohms and a lightning voltage of 200,000 Volts (In real world lightning can be a lot lot more than that) you will end with an electrical current of 2 Million amperes... for a very short time; some milliseconds, but enough to burn your gear, no matter how good grounded it is.

The trick is to route the strike around your equipment. How exactly? That's the question.....

My 2 Cents.

Regards

JB
 
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Re: best practice for lightning protection

Tue Jun 16, 2009 11:21 pm

I agree. Ohm's Law applies. 800,000 volts (that was what the lab used in the Tesla coil) through a resistance of 10^6 ohms (the average resistance of a tire) would produce a whopping 80ma. through the Faraday cage.

EDIT: My bad. 320ma. There are 4 tires! And the voltage potential of the Faraday cage to ground will be close to 800,000 volts during the strike. That is that "voltage ladder" thing.
 
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Re: best practice for lightning protection

Wed Jun 17, 2009 9:47 am

resistance of a tire, ok... where's resistance of an air? or an air is pure conductor for now?
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Re: best practice for lightning protection

Sun Jun 21, 2009 1:34 pm

resistance of a tire, ok... where's resistance of an air? or an air is pure conductor for now?
During a lightning strike, there is very little air in the electron stream. It has been superheated and expanded to the point that the electron stream creates its own "vacuum tube" with the walls held out by the air against the outer boundary of the stream. The thunder you hear is the electron stream ejecting the air.

Here is an interesting video. There is no Faraday cage for this guy. He is outside.
http://www.youtube.com/watch?v=9CUz8XNHbiY
Only a lack of ground prevents this guy from getting body parts blown off.
 
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Re: best practice for lightning protection

Wed Jul 22, 2009 7:33 am

SurferTim,

I'm just a few hours north of you - I understand (real world any way - your theory and understanding of electricity exceeds my own) what you have said and have had similar experiences. Nothing beats having little or no ground with a nice grounded lightning rod near by - even if you use AC for power with proper equipment.

I would like to understand the small solar system you setup though. Would you mind posting all the parts, maybe a small diagram and perhaps a photo of momma and company.

I believe if you are willing to share onlist would be best but if you would rather send directly to me thats fine. scott at brevardwireless dotcom

I have another question for you too... Forget solar and the lightning for a sec - if I just want to run my equipment off 12v or 24v dc battery and have appropriate 12/24 volt charger can I just hook radio equipment directly to battery terminals with fuse of course (also assume my equipment is made for given voltage) and plug in a small inexpensive smart charger from walmart (those terms may be mutually exclusive lol) and be done with it? I wonder about the way the output from the charger affects the routerboards if at all. I'm sort of thinking the radio gear would really be running from the charger output not really the battery and not sure if that will cause overcharging of battery because the smart part of the charger may get confused with the other equipment connected - or is it a non-issue. Thanks for your time.

Scott
 
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Re: best practice for lightning protection

Wed Jul 22, 2009 12:48 pm

Hi Scott,

The setup is very simple. I use Kyocera solar panels and Morningstar chargers (the one with the Low Voltage Disconnect). I am expecting the arrival of a new panel/charger this week.

I do have some battery powered units that are charged by AC, but I use marine type battery chargers (for sailboats while at dock). They are more expensive, but the ground is isolated to prevent galvanic action (stray electrical currents) from corroding the underwater metal parts of the boat. But what is important to me is it has no ground path for lightning. They are also designed to be connected to your battery 24/7, unlike some other not-very-smart chargers. The only drawback is the low voltage disconnect. It is almost as expensive to buy a Low Voltage Disconnect unit for these as a solar charger.

UPDATE: Yes, three severe thunderstorms later, and that roof unit is still working. Just lucky, I guess....

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