Lightning protection

there is no guarantee that a baseball cage is adequately grounded. the support poles are usually set in concrete.

faraday cages are meant to block RF. lightning is DC (mostly).

refer to

i routinely repair lightning damaged equipment. when you see first hand large molten globs of metal, ceramic, and other material that used to be perfectly good electronics you tend to get real cautious about where you go and what you do when a lightning storm passes through.

Effectiveness of protection from lightning is determined by how that electricity gets to earth ground. Not earth ground beneath you. If seeks charges via earth that is maybe miles away. In the process, the struck batting cage then carries electricity underneath your feet to to take a mile plus path to those distant charges.

For example, if standing on earth with feet apart, and if the nearby tree is struck, then electricity might pass through earth, up one leg, down the other, and then continue through earth. Therefore the human is electrocuted.

This is also why four legged animals tend to be at risk when a nearby tree is struck. Four legged animals do not make a single point ground connection to earth; therefore can be harmed by electricity flowing through the earth.

The baseball cage may act as a good lightning rod. But then electricity passes beneath a human to cause harm. IOW the faraday cage is not complete because the earth beneath the human was not sufficiently conductive.

BTW, lightn> Hi folks...this was in a baseball newsgroup that I participate

(maybe

Effectiveness of protection from lightning is determined by how that electricity gets to earth ground. Not earth ground beneath you. If seeks charges via earth that is maybe miles away. In the process, the struck batting cage then carries electricity underneath your feet to to take a mile plus path to those distant charges.

For example, if standing on earth with feet apart, and if the nearby tree is struck, then electricity might pass through earth, up one leg, down the other, and then continue through earth. Therefore the human is electrocuted.

This is also why four legged animals tend to be at risk when a nearby tree is struck. Four legged animals do not make a single point ground connection to earth; therefore can be harmed by electricity flowing through the earth.

The baseball cage may act as a good lightning rod. But then electricity passes beneath a human to cause harm. IOW the faraday cage is not complete because the earth beneath the human was not sufficiently conductive.

BTW, lightn> Hi folks...this was in a baseball newsgroup that I participate

(maybe

go

Yep, you never know. I hide under the bed myself.

N

utter and complete crap.

lightning is an electrostatic discharge.

Lightning is AC ?!!!. I've never seen any rotating clouds, in the UK we get plenty of lighning but no rotating tornados with lightning.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

With no mesh underfoot, it might depend on the shape of the cage. If you were surrounded on three sides, there might not be much current underfoot because the metal fence would be a better conductor. At the nearest playground, the "batter's cage" is just a wide V backstop, so I wouldn't stand there in a storm.

Pointy rods on the top of the cage might prevent a lot of strikes by bleeding off charges.

I think I've read that there can be several phases in a lightning strike, and maybe electricity flows back and forth. I can't remember. Anyway, lightning doesn't have to be AC for a power line to be a poor conductor. Inductance reacts against a sudden change in current. With lightning, the change is so sudden that a little inductance means a lot of impedance.

Leading from a 220V transformer to a house, the three conductors are usually twisted together nowadays. The reduces inductance. I'll bet we'd have less damage from surges with fast rise times, whether or not caused by lightning, if power companies spaced the conductors a foot apart as they once did.

Huh? Cite?

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To make it easier for some to understand, I should have first noted that lightning is an impulse. The classic current transient is an 8/20 microsecond impulse. That impulse is a summation of frequency components; AC waveforms at various radio frequencies. This is basic knowledge to those with electrical engineering training AND those with math backgrounds that include Fourier Series.

Lightn> w_tom wrote:

To all:

This statement is correct. A lightning bolt often consists of as many as

40 to 50 individual discharges. This is not apparent unless the lightning is captured by high speed photography.

So, since the lightning discharge turns on and off 40 to 50 times in a fraction of a second, it is not pure DC.

The current flows in only one direction. However, the energy is split between a DC component, and a considerable part that is effectively RF energy. Note this is RF energy, not low frequency AC.

I don't have a Web source to cite for this, but I have read about this before. Specifically, that a ground for a lightning rod must not go through a coil of wire.

Aidan Grey

as

through

chopped DC makes sense - anyone know what initiates the chopping and the rate of chop? Is chopped DC the discharge mechanism from van de graff's etc?

A small multiple of 40-50 Hz is not exactly RF. So what's the risetime of these pulses? Duration?

Why would you want one to run through a coil, anyway?

I suspect the warning is to avoid somebody being electrocuted by induced current from the pulse(s).

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Risetime of these current pulses was provided in a previous post: exponentially rising and falling edges of 8/20 microseconds.

Obviously the ground wire would not be run through a coil. But due to the high frequency nature of transients, that ground wire must not be spliced, no sharp bends, and not routed inside metallic materials. A violation would only increase wire impedance unacceptably. Why? Because even sharp bends cause significant impedance increases when discussing the higher frequency components of lightning.

We could play a game of 50,000 questions since even the most basic nature of lightning - its RF components - is new information. These and other questions have been answered previously in a list of citations at:

Figure about > A small multiple of 40-50 Hz is not exactly RF. So what's the

citing a newsgroup discussion is not a valid reference.

elaborate (and probably inaccurate) discussion as to the exact nature of lightning will not be of benefit to the original poster.

a DC pulse is still a DC pulse no amount of wishful thinking will turn it in to AC (granted that there are some aspects that generate RF and perhaps some other characteristics that may be able to be handled by AC analysis)

looking at a few of toms 16,900 archived posts i see he also claims that a ground rod in rock will make a perfectly good ground. from that it follows that a batting cage set in concrete is adiquitly grounded. i dont think so.

That a pulse is susceptible to Fourier analysis does not make it "contain numerous AC sine waves."

Much of that energy is in the 100 kilohertz and Megahertz

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I took what you wrote previously to be the pulse duration, not its risetime.

An 8 microsecond risetime doesn't imply all that high a frequency. Sharp bends in thick wire at ultrasonic frequencies aren't a big deal.

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You are joking. Right? The Fourier analysis of lightning reveals energy at numerous frequencies. Lightning is RF electricity. That RF energy is why lightning even causes noise on radios. So now you say all those RF sine waves, demonstrated by Fourier analysis, really do not exist? Why not just say the world is still flat? If lightning did not have so much energy in RF, then radios would not receive that RF noise. An example that demonstrates the RF nature of pulses and of lightning. Pulses are not DC.

If lightning were DC, then wire impedance would not be relevant. But lets put numbers to it. A 50 foot 20 amp wire may be 0.2 ohms resistance. But wire reactance means same wire has something like 120 ohms impedance to a lightning transient. Why is impedance so much larger than the resistance? Because the RF components of lightning make impedance relevant and significant. If lighting were DC, then wire resistance and wire impedance would be same. If lightning were DC, then lightning would not have such destructive consequences.

Fourier analysis demonstrates lightning is AC electricity at many frequencies. Putting a number to the impulse - 8/20 microseconds - explains why so much energy is in the Megahertz range. Using DC analysis to explain lightning means that person never first learned basic transient analysis taught to first year EE students. Lightning has massive energy in radio frequencies which makes lightning so uniquely destructive. Those radio frequencies even mean that an earthing wire bundled with other wires will induce transients on those other wires. DC electricity would not do that inducing.

Why are induced transients a problem with lightning? Because lighting is AC electricity - as demonstrated by Fourier analysis, as demonstrated by discussion about impedance, as demonstrated by what first year EE students are taught, as demonstrated by noise on the radio, and as demonstrated by so many industry professional cited in:

Show me. Show me how lightn> That a pulse is susceptible to Fourier analysis does not make it

Point one. Deny citations from industry professionals by refusing to read them. An ostrich does that; not an informed human. Cited are numerous technical papers and other technical facts on lightning - literally a full days worth of reading. Instead TimPerry pretends those citations did not exist in:

A DC pulse is an oxymoron. As confusing as another ridiculous term: DC triangle wave. Either it is a pulse affected by reactance (inductors and capacitors), or it is only DC that completely ignores reactance. One cannot have it both ways. Either it is DC that ignores reactance, or it is a pulse that makes reactance relevant. Which is it? If lightning is DC, then inductance, capacitance, and impedance is not discussed. Why do industry professionals discuss these repeatedly? Because lightning is not DC.

Pulses are transient responses - taught in 1st year engineering - an introduction to AC characteristics. AC analysis makes wire inductance and capacitance significant. DC analysis ignores inductance and capacitance. To understand how lightning works - as cited in

- one cannot pretend lightning is DC. A lightning impulse is an AC or transient event. Lightning is a composition of many frequencies. Show me a DC wave that has frequency components? You cannot. That is the oxymoron of DC pulse. A 'pulse' has AC components. 'DC' has no AC components. Oxymoron.

Equally confusing is to say "DC triangle wave". DC pulse or DC triangle wave - both are oxymorons. Both contain numerous frequency components. Therefore a 'DC pulse' cannot be analyzed using DC analysis. Lightning requires AC analysis. Lightning is not a DC event.

Point two. TimPerry believes a batting cage set in concrete is not conductive. TimPerry should first read those discussions he refused to learn from in:

A most superior earth ground is an Ufer ground. Why? The earthing is through concrete. Had TimPerry first learned what industry professionals teach, then he would have known the batting cage mounted in concrete makes a best earthing ground

- exactly like Ufer grounds. But then TimPerry also promotes an oxymoron called 'DC pulse'. Somehow he knows without first learning the facts. If only he had first read those citations and first learned about Ufer grounding. Then he would not have posted, "i dont think so." One should first learn before knowing something.

The energy of lightn> citing a newsgroup discussion is not a valid reference.

well I'd never even thought about whether it was AC DC or whatever. But its an interesting discussion... Its certainly disruptive across a wide band of the rf spectrum. I wouldn't make a phone call if it was overhead anyway! hmmm