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.
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.
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'
There was a 2 part article on grounding of lightning currents.
Part 1 does not seem to be available. Information includes
- the spectrum for the most common waveform has most energy below 100kHz with some out to 1MHz.
- large down conductors are not for heating effects but are for strength from magnetic forces with high currents heating effects at terminations continued effectiveness with oxidation and corrosion over time resistance to mechanical damage
Part 2 is available several places including
Whatever you say. You are obviously MUCH smarter than the lightning protection engineers that design the stuff.
Then why are there at leat 3 kinds of "stranded" cables for ligtning protection? Standard twisted, rope laid, and woven??????
Yes - and more surface area for cooling - and with the interwoven braid of the "woven or braided" cables, a self cancelling of the magnetic field as the conductors run in opposite directions around the air core - in the case of the braided cable. The braided cable acts as an air-core inductor with opposing windings - whatever effect that might have.
You do not understand in the slightest what you just did.
You built up a magnetic field in an air-core coil and quickly collapsed it. The rapidly collapsing high intensity magnetic field induced a very high voltage in the coil. The voltage induced is determined by the strength of the magnetic field, the speed of the collaps, and the number of turns in the coil.
The 48 volt battery pack could not supply anything more than the 48 (or 50.5) volts the open circuitted batteries normally produce, into the circuit. It had nothing to do with "trying to supply 500 amps"
Clueless.
And if you make the conductor too wide, the capacitance to ground also increases - affecting the impedence.
When you hear lighning interference on the radio, is it just a SNAP
- which would be all you get with straight DC?? No, it is a crackle/fizz typical of an alternating current of high rate of rise/decay ( I forget the term - something like dldt but that's not it)
Where does he disagree with the "engineers that design the stuff"? Are you using your Ouija board again?
Why do you think there are 3 kinds? Cite?
From part 1 of the article I cited - large down conductors are not because of heating effects.
About a #6 wire will have a 50 degree C rise with a 175kA standard surge. That is way toward the high end of lightning strikes.
A non-inductive wire. What a wonderful idea. Cite from someone in the real world.
The article I linked to missed it entirely.
Not obvious what "loosely coiled on the floor" is. Doesn't sound like much of an inductor to me.
Wire has an inductance. If there is a large current in the wire that is suddenly interrupted there is a surge at the fuse. One source of utility surges is fuse action. High fault currents stores energy in the magnetic field of supply wires. When the fuse opens the magnetic field collapses and there can be a damaging surge at the fuse - and anything connected near or beyond. It is rather well known.
The inductance of the wire tries to continue the fault current. It is what inductors do when current is interrupted.
I agree with what Robert has written and it is consistent with the article I linked to.
Clueless
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.
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.
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:
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?
Repeating
*WHY* do you think there are 3 kinds? Cite?
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.
EXACTLY! Lowering the impedance further.
The currents flowing in a ground plane even at DC are interesting but for a transient become even more interesting. There are currents flowing in what you would consider the 'wrong' direction. Adjacent to the currents flowing in the 'correct' direction. As you may know a current in one direction [the main current flow] having currents next to it flowing in the 'wrong' direction [one enhances this effect by making the connection much wider than what seems necessary] cancels magnetic fields and really lowers the impdeance that the main current was 'seeing'. For exmple, consider the impedance between 2 points one inch apart in the center of a ground plane that is first only 1.5 by
1.5 inches, then compare to impedance between the two points when the ground plane extends out further to 4 by 4. Map the currents flowing. Very educational.The allegory I mentally use to envision a discharge and makes it easy [easier] to understand lightning discharge is envision a rubber sheet. That is ground. Then pinch a small bit and lift up. that is like a lightning strike at the point where you pinched the sheet to llift it. It is easy to see that with uniform impedance around [the rubber sheet] the slope of the fields created by that discharge. You have like a teepee. And, you can see how there is very little voltage difference between adjacent points. Also, see why four legged animals are more likely to die than two legged animals from an adjacent strike. Now violate the uniform impedance of the rubber sheet by running conductors around. Unless those conductors are concentrically placed around the hit they will transfer high voltage gradients unintentionally between two points of widely varying voltage and since high voltages occur across very narrow regions SECONDARY discharges will occur.
A bit clumsy allegory but helps sometimes to envision the voltage gradient aspects of lightning.
Also, from experience of discharges in air. It is very difficult to get a super fast rise time of a discharge against a 'point' surface. A broad flat surface makes a blast discharge for the same amount of charge build up that a pointy surface produces. Thus, IMHO lightning rods can be made to work as protection and can be much better than nothing there at all.
My understanding that it is cheaper and more effective when drawing up from 5,000+ feet.
You're wasting your time... Go get a girl friend..
The predominant posters on this website do no recognize your expertise as being meaningful...
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.
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.
From personal conversations with the lightning expert from the Univ of Wisc= onsin electrical engineering department,
the wave form of the lightning strike is a damped sinusoid and the cable ne= ed only be #10 wire. =20
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 w= ith 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.
That works on 10Bt and 100BT - pretty difficult on 10B2 (co-ax)
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.