Did Lightning Rods do any Good?

Page 3 of 4  
wrote:

Read the cites I gave a couple of days ago. There are actually MORE than 3 kinds - but 3 major types. I gave the links to 2 major suppliers.

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On Jan 26, 9:25 pm, snipped-for-privacy@snyder.on.ca wrote:

Here are some of your statements and some questions:
"Whatever you (Robert) say. You are obviously MUCH smarter than the lightning protection engineers that design the stuff. "
What exactly has Robert Macy said that is inconsistent with what lightning protection engineers say?
"ALL of the farm lightning rod systems I've ever seen have used the looase braid copper cable.(Class 1)
See: http://www.kuefler-lightning.com/series100-conductors.htm OR: http://www.tlpinc.com/products/conductors/copper-conductors/main-size ... "
The two supplier links you yourself provided clearly offer lightning conductors that are *not* braided as well as those that are braided. They are right there on the link next to the braided ones. That would surely seem to suggest that despite what you might or might not have seen, braided conductors are not used exclusively. So, what exactly is your point?
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On 1/26/2013 8:25 PM, snipped-for-privacy@snyder.on.ca wrote:

Repeating *WHY* do you think there are 3 kinds? Cite?
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Interesting that with that cabling one only gets 50C rise for that much current, but at least not enough to ignite anything. My experience with ESD discharges [inside confined electrical systems] is that the energy is approximately centered around 3MHz, extending very energetically up beyond 30MHz, and in poorly designed systems above 100MHz. These ESD events are those little 'arc overs' in the 20kV, up to 150kV systems.
I was surprised the coil's inductance measured around 50uH
But, I shouldn't have been surprised since a six foot length of Belden Hospital grade AC line cord is a three winding transformer with a core impedance measured approx 7uH. [That was from memory, may have been 1.7uH, 7uH seems a bit high, suggesting 100nH/in, where the usual is only 10-20nH/in] If interested, a few years ago I posted the model for the AC cord named with the Belden part number in the LTspice group, along with a couple of standard LISN models.
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On Sun, 27 Jan 2013 07:26:07 -0800 (PST), Robert Macy

A software developer I used to do contract work for had all kinds of problems with their 10B2 ethernet network. Collision rates and dropouts were HORRENDOUS. I found 50 foot rolls of co-ax coiled up behind desks in a few spots, and MANY 15-25 foot rolls - "just in case they wanted to move the desks". I took out all of those "air core inductors", replacing with cables jus a foot or two longer than absolutely necessary, and the network speed and reliability improved very significantly.
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On Jan 27, 12:04 pm, snipped-for-privacy@snyder.on.ca wrote:

Well done! There is a way you could have kept all those cables and had the best of both worlds. [as long as you didn't exceed maximum distance] by using ferrite clamps on the cables. Just place every foot along each cable and that would have destroyed the 'transformer' effects. However, at $1/ea they probably would have opted for the shorter cables.
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From personal conversations with the lightning expert from the Univ of Wisconsin electrical engineering department,
the wave form of the lightning strike is a damped sinusoid and the cable need only be #10 wire.
Now, nobody ever installs them with wire that small. It's counterintuitive. But this professor could back up his statements both with the math and with experience.
Some of you who've been around usenet a long time may remember some of the arguments over lightning striking cars. Yes, it protects, via the Faraday cage effect, but cars seem to get hit less often than they should, so maybe the shape is protective in some way.
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That reinforces my use of 8 gauge. But my split tree makes me wonder.
Greg
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On 1/28/2013 11:03 AM, TimR wrote:

But this professor could back up his statements both with the math and with experience.

Part 1 of the article I linked to (which is no longer on line) has temperature data for wires. A #10 wire has a 200 degree C rise for a 100kA lightning stroke. About 5% of strikes are over 100kA, and there can be multiple strokes.
#10, or the house it is attached to, is likely to have problems in Florida.
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A related factor, I would think, would be the voltage drop across the wire. Assuming your 100ka strike, a 50ft run of 10gauge would develop 5,000 volts. A 50 ft run of 4gauge would develop only 1,200 volts. At the higher voltage, the likelihood of the strikie flashing over to something other than the desired wire increases.
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On 1/29/2013 10:48 AM, snipped-for-privacy@optonline.net wrote:

But this professor could back up his statements both with the math and with experience.

I assume that is based on resistance.
Lightning is a very short event which means it has relatively high frequency components (from a previous post most of the energy is below 100kHz.). That means inductance is likely more of a problem than resistance. Also skin effect. Larger wire has a major effect lowering resistance, but not much effect on inductance and skin effect. Both are covered in a link I posted.
Downconductors are #3 or larger. They are that large for reasons also in a previous post.
================================================For power wiring, the 1968 NEC had correction factors for skin effect on large wires. I don't know when the tables were dropped; the correction was probably rolled into the other tables. The AC resistance of a 4/0 wire is increased by about 0.5% over the DC resistance. The diameter of a 4/0 stranded conductor is about 0.5".
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On Mon, 28 Jan 2013 07:32:06 -0800 (PST), Robert Macy

That works on 10Bt and 100BT - pretty difficult on 10B2 (co-ax)
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On Jan 28, 12:01 pm, snipped-for-privacy@snyder.on.ca wrote:

Actually will help
prevents signals fromgetting onto the shield and then 'injecting' themselves inside to the center conductor. Also makes the coax 'higher' quality.Work on analyzing 'shield induced' noise may appear somewhere. The beads help prevent that.
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On Mon, 28 Jan 2013 16:46:37 -0800 (PST), Robert Macy

I read you wrong - I thought you wanted to put a ferrite clip on the COIL..
The co-ax wasn't the beast quality stuff either. The owner was a millionaire - which equates to "one cheap b@$r@rd".
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On Jan 28, 5:54 pm, snipped-for-privacy@snyder.on.ca wrote:

hey, one accumulates money by bringing it in, and NOT letting it out.
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On Jan 25, 11:00 am, snipped-for-privacy@snyder.on.ca wrote:

Thanks. Robert always thinks his opinions are better than anyone elses standard usage.
Most of what we used was the Thompson smooth weave. It made down conductors easier to form in smooth turns/angles that met specs. Not being smooth turns invited the lightning to jump off the cable to nearby surfaces. That's more proof why it travels on the cable surface rather than deep.
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Actually that effect has nothing to do with whether the current is traveling near the surface of the conductor or not. It's due to the fact that sharp bends increase the impedance of the conductor which becomes significant with the fast rise time of a lightning strike. As the impedance goes up, it becomes more likely that the lightning surge will find another path to ground.
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One has to follow what one thinks. If proven wrong, then change that thinking.
I have ALWAYS looked very closely at the empirical facts. After all, science DESCRIBES observation, and does not DEFINE it.
What I described does NOT refute the installations you're familiar with, rather supports them. Just modifies some of the underlying principles, that's all. For example, skin effect of the cable requires the cable to be large diameter to be effective - which it is. Flexibility during installation requires the cable to multi-stranded - which it is. I just pointed out that one should not go on to claim that somehow multi-stranded is approximating what is known as a "Litz wire effect"
In those Class I cables for installation the skin effect does force the conduction to the outside surface of the cable, and akin effect's increase in impedance actually justifies using the 'smooth' weave to maintain lowest possible impedance. Not a bad compromise at all.
Just make certain that the grounding goes to ground and not to something 'floating' above ground. There was an oil field in Kansas that kept losing their down hole pumps due to lightning srikes. They had all the 'right' protection possible around them but still during heavy storms, they kept losing a pump. That means NO OIL, bring out a rig, pull up the pump, replace - not cheap! pumps are what size? bore diameter and almost 20 feet long?
I could NOT find anything wrong with their protection techniques, and during pure frustration I started chatting with one of the drillers, who decried that these wells were 'cursed' from the day they started drilling, especially that damned wet salt layer they hit about 500 feet down. Say what!? Now just envision a large conductive salt layer covering several square miles down around 500 feet. Any 'grounding' you do up here on the surface is 'floating' in comparison. Solution - drill down to the salt layers, ground all to that layer and problem solved.
Lesson is 'never assume' and 'always listen'
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On 1/26/2013 9:52 AM, Robert Macy wrote:

At least one manufacturer of submersible water pumps puts surge protection in the motor.
[I thought all oil well pumps were powered by surface walking beam.]
How do you connect to the salt layer given inductance of the conductor and distance? I would think if the wells were steel cased to the pump, the casings would not even work real well as a conductor.
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My understanding that it is cheaper and more effective when drawing up from 5,000+ feet.
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