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View Full Version : Fun with Static Electricity (or go fly a kite)



DyerWolf
2007-Oct-15, 08:17 PM
When I was in Kuwait there was nothing to do.







For a long time.








One day we had a sand storm.

After several hours, some of my Marines decided to fly a kite. They took a poncho liner (5' x 7' nylon blanket) and tied parachute cord to three of the four corners. Because they ran out of nylon cord, they used comm wire (thinly coated wire) for the fourth corner.

They got the kite up in the air about 200 feet.

Anyone know what happened next?

After flying the kite for a while, the devil dog holding the the comm wire yelped and dropped to the ground. He was out for almost 30 seconds and got 1st degree burns on his hands.

There was no thunderstorm activity - so I presume we have a static electricity event. My question: anyone know what the process would have been? Did the static electricity just build up in the nylon until it could ignore the wire insulation and zap the Marine, or did some other process occur?

tdvance
2007-Oct-15, 08:35 PM
I don't know, but a sandstorm sounds like a good place for static electricity to build up. (actually, is there ever lightning in sandstorms?).

Or, any voltage difference "up there" versus on the ground would do it.

Todd

alainprice
2007-Oct-15, 08:36 PM
Pure speculation:

Your marine was struck by a static discharge(can a discharge be static?) in the same way a lightning bolt is formed. He instigated it, but oh well.

Luckily, this one originated from 200 feet up, therefore the potential for destruction should be a lot lower.

The lesson is, ground your kite!!!

publius
2007-Oct-15, 09:18 PM
There was no thunderstorm activity - so I presume we have a static electricity event. My question: anyone know what the process would have been? Did the static electricity just build up in the nylon until it could ignore the wire insulation and zap the Marine, or did some other process occur?

Long wires in the wind are bad idea for this reason. :) I suspect it charged up enough to cause a breakdown of the insulation -- communication wire insulation isn't all that great. The insulation on standard electrical wiring is generally rated 600V (save for a few that are only rated 300V). 600V is the traditional cut-off between "low voltage" and "high voltage". I'm certified for the former, but not the latter. With the latter, you don't just splice wire willy nilly -- you don't like sharp points on your insulation, such as what you get when you strip wire with wire strippers -- transistions need to be smooth. HV wiring is an art:) Communication wiring (like phone and LAN cable, etc) are "low voltage". I'd have to look up the specs to be sure, but I think that's 50V max rating.

Generally, if something is an obvious insulator, it's generally good to a kV or two (but not officially, mind you, and might degrade over time). Above that, stuff happens. And I imagine that's what happened there. There was a breakdown event, perhaps helped by the mechanical stresses of bending and flexing of the wire.

There is also a vertical electric field in the atmosphere in fair weather. If you string a long wire up high in the air, and the more surface area of conductor exposed the better, you can get a pretty decent voltage to ground there, a couple hundred volts not being unheard of. Low humidity and abrasion like with a sand storm make it worse.

Actually this is one of the main reasons for "earthing" power lines (if you get me started on this, I'd ramble for ages, but I like to maintain a distinction between "ground", a good conducting, high capacitance, reference and safety feature, and that of making a connection to the dirt, terra firma itself), and lightning protection which is sort of the same thing.

A floating system, not connected to earth, would tend to build up large static voltages to earth, more than enough to stress and breakdown insulation. Tie one side or point of a multi-wire/tap system to earth, and you drain it off, and maintain design voltages to earth.

-Richard

publius
2007-Oct-15, 09:50 PM
(can a discharge be static?)

In a strict mathematical sense in a Maxwellian context, static means nothing is varying with time, and all time derivatives are zero. The wave equation becomes a Poisson equation, and E and B are "decoupled".

However, a more practical defintion of electostatics is electrical phenomena involving a charge separation due to mechanical or other means (you drag your shoes across the carpet). When a current is allowed to flow, the charges equalize quickly, and the voltage dissipates. It is generally a HV, low (and quick) current.

This is opposed to a more "dynamic", non-conservative source of EMF, which can drive a continous current loop. Generators (and yes, batteries) fall in this category. These are generally LV (relatively speaking), high current regime.

-Richard

publius
2007-Oct-16, 12:22 AM
Related to this, when a helicopter is going to land on a ship deck, or lower a cable to pick someone up or drop someone off, they always drop conductor cable with a lead weight to make contact first. And they have to make sure nothing flammable is around that contact point. The voltage difference can be quite large and the discharge can be powerful.

There was some concern with fuel drums and these plastic and other non-conducting bedliners in pickups, which have become quite popular (they are with me). You might have a metal fuel can or tank, say for your lawnmower, and it builds up a charge in the wind while driving. Since the bedliner insulates it from the body of the truck, you can get a spark right when you put the (grounded by law and inspected) fuel nozzle in contact with the can.

There have been several fires with severe burns blamed on this. You might say, hey, vehicles have "rubber" tires, so shouldn't this be a problem anyway? Well, those rubber tires, while they wouldn't carry a noticeable current at say 120V, are nonetheless conducting enough to quickly bleed off static charge, and even then, some conducting contact, like with your own body, will usually be made between the vehicle frame and ground before the fuel nozzle makes contact.

There is little danger with plastic or otherwise non conducting fuel containers, but metal ones, which can act a little capactor to rapidly discharge, are the concern. Always ground that out to the frame or attach a little jumper.

-Richard

Neverfly
2007-Oct-16, 01:55 AM
We had this issue in the Army with metal fuel cans. Eventually they were all replaced with plastic.
Had to always ground first.

Also, in the Gulf, we had chem labs. Had to hook a cable to a rail upon entry to bleed off static charge.

publius
2007-Oct-16, 07:24 PM
While on the subject of launching long wires into the air, I can't believe I forget to mention the Univerity of Florida's lightning research center.

http://www.lightning.ece.ufl.edu/

Those guys are figuring stuff out. And Florida is the place to do it. Florida is home to Lightning Alley, and area that gets the most lightning activity in the country.

One of the tricks they've learned to do well is to trigger a lightning stroke. The energy of natural lightning is a wee bit larger than what can be achieved in the lab, not to mention safely handled in said lab, and that's one of the obstacles to deeper understanding of all the details.

The ability to trigger a natural lightning stroke where you want it (most of the time) allows you to study it (from a "bunker" that's probably the world's best Faraday cage).

The do it by firing a little rocket trailing a wire. That acts as an artificial ground streamer that makes contact with an incoming cloud leader. The trick which they've learned to do, is to determine when a cloud leader is in range. They do that by measurements of the local electric field and other variables.

So just keep the above in mind when you get the urge to send long wires up into the air. :)

And besides pure research, there's also good practical applications for lightning protection and the effects on power systems(an electric power consortium helps fund the work). What better way to test the ability of something to take or divert or otherwise withstand lightning that to test it with the real thing.

-Richard

publius
2007-Oct-16, 07:38 PM
Be sure and click on the "publications" link to see the fruits of their labors there. I read that and laugh when I think of a certain vocal group known to frequent here that says the "mainstream" doesn't know or care much about electrical phenomena. :lol: I mean, heck fire.

Now, after looking at those publications, I'm getting wistful thinking about what might have been. Yes sir, if things had been perhaps only slightly different, I might have been down there. And I'd be in hog heaven. Ever since I can remember, the blue fire has always gotten me excited. The bigger the better.

When I fired that rocket and got a big flash, I'd yell "Heeeeeeee hawwwwwww!" every time.

-Richard

publius
2007-Oct-16, 09:08 PM
http://www.lightning.ece.ufl.edu/PDF/Gammarays.pdf

That looks interesting. They say they observered gamma ray production with their triggered lightning. That is a field of active research.

No sadder words of tongue or pen that that which might have been. I would be having ball there. Note the above. They've observed "energetic radiation" in 51 out of 63 triggered lightning events where they've been watching for it. And X-ray and gamma ray production seem to be very different.

The X-rays seem to occur as the cloud leader is coming down, and maybe briefly during the main return stroke. However, the gamma rays seem to come later.

PS: Darn it, this is interesting. They know they saw gammas, but they're not sure *where* they came from. Was it from the arc path itself, or way up in the cloud? And I note they say if the source was a couple of km high, which was possible, that would be a very large flux of gamma rays, quite biologically signigicant for something close by!

-Richard

Kaptain K
2007-Oct-17, 03:20 AM
Back to "wires in the air". Back in the 60s, when I was a teen, I flew control-line model planes. All but the smallest fly on a pair of braided steel wires. I remember one day at the local flying park when a plains thunderstorm (this was in Kansas) blew in. Everybody was trying to get on more flight in before the storm hit. As it got darker, people started getting light shocks from the control handles. One guy decided that the "solution" was to wrap a towel around the handle to insulate himself. When the charge built up enough to jump the towel, the spark nearly knocked him off his feet! I was "smarter" (yeah, right). I took my shoes off, kept one finger on the wires and flew very low. Yeah, I was very lucky (we all were). Like Ben Franklin was with his kite!

publius
2007-Oct-17, 03:36 AM
Kaptain K,

What's that old song, "Flirtin' with Disaster"? And what's worse is generally the most lightning activity occurs on the edges of the thunderstorm, rather than right underneath it. Generally, mind you. So the odds of getting struck are higher when it's off in the distance coming in or going out. The latter is when many people get hit. They think the danger is over after the cloud has passed. But it's actually higher.

Just look at those photos of the triggered lightning hitting the launch tower, with the wire vaporized. That could have been you on the end of that. Those little shocks were just baby stuff off to the side. If the main deal had wandered over in your airspace, you would've ridden the lightning. Literally.

-Richard

Kaptain K
2007-Oct-17, 03:42 AM
Don't I know it! Looking back, I'm amazed I survived my teens (and 20s for that matter).

publius
2007-Oct-17, 03:45 AM
Don't I know it! Looking back, I'm amazed I survived my teens (and 20s for that matter).

We all are, we all are! Youth is wasted on the young to coin a phrase. :shifty: Just imagine what we could do if we had our current wisdom and experience with our youthful bodies.

And somewhat relevant, the words of another song: "Thunder's just the noise, boy, it's lightning does the work." The theme there was talking vs. doing. :)

-Richard

Kaptain K
2007-Oct-17, 04:10 AM
Marriages are made in heaven...
...So are thunder and lightning!

publius
2007-Oct-17, 04:14 AM
Guess I should tell you about my own flirting with lightning riding. As a bright young wise fool of around 19 - 20, I got fascinated with the heavy lightning of an approaching thunderstorm. I stood out on the front porch and watched. It was beautiful, and I was thinking about all the stuff going on there.

It was getting closer, and darker, but out there on the porch I stood, just watching. The event occured so fast it all blurred together. There was a brilliant white. I mean complete white out. The sound, well it was more shock wave than sound. Sort of like having your ears slapped with a two colliding pieces of tin. I fell down on the porch floor, and nearly emptied the contents of my bowels into my underoos.

I was blind. And deaf. Talk about arc flash. It was orders of magnitude more intense that any relatively dinky little things since. It happened so fast, I only consciously realized what had just happened while I was lying on the floor, ears ringing and blinded.

I thought that strike must've been right there in the yard. It wasn't. It hit a tree close to 300' away. Now, when I realize that if it was that bad 300' away, what would it be like 30' away, or worse. Ever since, I seek cover. Better to watch it on TV. That's called learning the hard way, of course. :)

-Richard

DyerWolf
2007-Oct-17, 12:39 PM
We all are, we all are! Youth is wasted on the young to coin a phrase. :shifty: Just imagine what we could do if we had our current wisdom and experience with our youthful bodies.

...

-Richard

Hopefully all of us live long enough to regret things from our youth. In fact, I pity the person who didn't do anything while young worth regretting as they get older.

Builds character - and makes for good stories / memories as well!

tdvance
2007-Oct-17, 05:17 PM
As a child, I sat on a radiator during a thunderstorm. uh--I never did that again!

Todd

DyerWolf
2007-Oct-17, 06:02 PM
I have had my own close calls with lightning. I really enjoy thunderstorms, and have always found them * ahem * electrifying. I much prefer to see them in person.

One of my favorites was a time when I went surfing in a storm as a teenager(my mother asked "you're not going out in the rain, are you? - snappy relply: Can't get much wetter surfing..."). While out on my board a bolt of lightning hit about 300 m away. The entire sea around the impact point glowed turquoise for a few seconds.

Anyway the waves were awesome. (4-8 foot in sets of 3) I came in after the leading edge passed and the wind blew the waves out.





I've always relied on the "and" in the description of who God looks after!

DyerWolf
2008-Jan-15, 02:25 PM
Seems the blowing sands carry quite a charge...

Link (http://www.foxnews.com/story/0,2933,322585,00.html)


Sweeping sands across the Sahara and other dune expanses are blown by more than just wind, scientists have discovered.

Powerful electric fields spring up near the desert floor and propel sand grains into the air.

...As wind forces sand to scrape over Earth's surface in a process called saltation, the friction causes the sand particles to pick up loose electrons from the ground, giving them a negative charge and leaving the surface with a positive charge, the researchers found....

"It's sort of like when you stroke your cat and feel little sparks, or run a balloon on your head to make your hair stand up," said Jasper Kok, a graduate student in applied physics at the University of Michigan...

...The separation of charges creates an electric field that can reach strengths of 100,000 to 200,000 volts per meter at a centimeter from the surface.

No wonder my Jarhead-DevilDogs got knocked off their feet.