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#1
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Lightning Strike OT? WTH brought this on?
So I read this thread with great anticipation of seeing how it relates to
the subject of this newsgroup! Let's all collectively compliment all these snooty astro-phycists on their deep knowledge and ask them to go back into their laboratory so that we can continue to enjoy our hobby! Just my 2 cents. -- _______________________________________ "The difference between 'involvement' and 'commitment' is like an eggs-and-ham breakfast: The chicken was 'involved' - the pig was 'committed'." http://community.webshots.com/user/godwino "Dave Bell" wrote in message ... On Sun, 27 Jul 2003, w_tom wrote: Let's review where all that energy was applied and how much - with numbers so that we don't do what junk scientists must do. Don Kelly in Newsgroup sci.physics.electromag on 4 Nov 2000 entitled "Oddball question": over the duration of the storm (and a wide area) ... A typical stroke will reach its peak in about 1-2 microseconds and die to about half peak in 50-100 microseconds. Millionths of seconds, not seconds! There may be several strokes in the same path but even 3-5 strokes will take less than 1/1000 second. The strokes just appear to last seconds. Yes there is a high peak power in a stroke but this does not translate into appreciable energy (about 55 KWH (200MJ)for an average stroke). Energy is what we need, not high peak power. Which, for "Gee Whiz!" value, works out to on the order of 2x10^12 Watts over 100 uS... The US Army defines in TM5-690 a wire size sufficient to discharge lightning without damage. 10 AWG. This makes complete sense once one learns a direct lightning strike has so little energy. Various non commercial websites suggest that a typical lightning strike releases 250 KWH of energy. A big one may release 10 times that much. That is a lot of energy. Admittedly, most of that is dissipated in the air above where it strikes, but I think it is disingenuous to characterize it as "little". A lightning rod above the pond and properly earthed by 10 AWG or heavier wire is more than sufficient to intercept and divert lightning to earth without pond damage. Most lightning rod manufacturers use 2 or 0 gauge wire as the down wire. 10 gauge seems to me a little flimsy. Given that a 10 gauge copper wire has a resistance of about 1 ohm per 1000 feet, and given a total length of wire of about 50 feet, we are dealing with 0.05 ohms of resistance. Given also that an average lightning strike can have a current of 10,000 amps (NASA has measured at least one strike of 100,000 amps)(and that the conductor takes the entire current) we are dealing with a dissipated power of 10000^2*.05 or 5 million watts. Or 100,000 watts per foot of wire. Admittedly this is for a very short time. But I submit that 100000 watts applied to a foot of this wire over a millisecond will melt or otherwise seriously damage that wire. In addition to the DC resistance, you need to take into account the inductance of the grounding wire. In the far more limited world of industrial high energy discharges, an associate observed multiple instances where a large laser flashlamp power supply was dumped to the solid copper lab grounding grid. The cable from the crowbar switch to the grid was about 4 feet long, running perhaps 30 degrees off the vertical. They would see sparks "shortcut" from 18 inches or more up the cable, to the floor, rather than continue down the direct path. What's the dry air breakdown voltage for 18 inches? These *potentials*, with significant energy behind them, do occur, even with properly grounded equipment! Dave |
#2
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Lightning Strike OT? WTH brought this on?
Just Me \"Koi\" wrote: So I read this thread with great anticipation of seeing how it relates to the subject of this newsgroup! Let's all collectively compliment all these snooty astro-phycists on their deep knowledge and ask them to go back into their laboratory so that we can continue to enjoy our hobby! Just my 2 cents. actualy it started ontopic as some ones pond got blown out of the ground by lightning John Rutz Z5 New Mexico never miss a good oportunity to shut up see my pond at: http://www.fuerjefe.com |
#3
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Lightning Strike OT? WTH brought this on?
And I, for one, enjoyed the reading. Learned something I didn't know as I
thought my expensive surge protector would protect me from Wind, Rain, Floods, Lightning, the dark of night and the boogey man! ~ jan ("my ten cents, my two cents is free") ;o) Just Me \"Koi\" wrote: So I read this thread with great anticipation of seeing how it relates to the subject of this newsgroup! Let's all collectively compliment all these snooty astro-phycists on their deep knowledge and ask them to go back into their laboratory so that we can continue to enjoy our hobby! Just my 2 cents. actualy it started ontopic as some ones pond got blown out of the ground by lightning John Rutz Z5 New Mexico never miss a good oportunity to shut up see my pond at: http://www.fuerjefe.com See my ponds and filter design: http://users.owt.com/jjspond/ ~Keep 'em Wet!~ Tri-Cities WA Zone 7a To e-mail see website |
#4
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Lightning Strike OT? WTH brought this on?
As a result of same discussion in another newsgroup, another
added this somewhat related information: www.tinyurl.com/buus "~ jan JJsPond.us" wrote: And I, for one, enjoyed the reading. Learned something I didn't know as I thought my expensive surge protector would protect me from Wind, Rain, Floods, Lightning, the dark of night and the boogey man! ~ jan ("my ten cents, my two cents is free") ;o) |
#5
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Lightning Strike OT? WTH brought this on?
wtom wrote
www.tinyurl.com/buus I don't think anyone has figured out how to put one on a koi yet. k30a yearly brother website posting http://www.30acreimaging.com/ |
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