Just a thought - as the panels have a lot of metalwork and are presumably at earth potential what are the added lightning risks?. Will they "attract" lightning? If so, then should they have a heavy earth cable into a ground rod?
Negligible compared to your TV aerial if you still have one!
Martin Brown wrote in news:5_TJt.51341$ snipped-for-privacy@fx27.am:
Mmmm! But is an aerial as "earthy"? Also, is the co-ax so light that it would vapourise without conducting too much current??
We don't really do grounding of TV aerials in this country like they do in other jurisdictions, eg USA.
Clearly the laws of physics are different abroad.
In article , DerbyBorn scribeth thus
Hardly any more then what they already are. Your average lightning discharge has usually travelled a few miles, runs at millions of volts and at tens of kilo-amps so a bit of wire on the roof?..
What usually happens is it will take whatever route or routes it can find to get to ground wherever they are. TV aerials usually get vaporised particularly the aerial cable. Bricks can be blown out of walls, light and power circuits can be very seriously damaged and so on;(..
What a decent lightning conductor does is to SHUNT the lightning currents past the house to Earth thus giving it a very direct path to Earth.
Normally done with a Copper or Ally earthing "tape" some 1 inch by eighth and a few deep driven electrodes info the ground. This needs to be a lot more substantial then the usual rod for earthing purposes. The lightning conductor needs to be of as low impedance as possible even a kinked bend around a gutter can present a point where the current can arc over!..
After that grim diatribe you might like to read a section on the Furse website that outlines the protection of PV systems!..
After that post, I wonder if you-know-who (as in my sig) will be back...
Lightning will strike tall objects. If you house is higher than surrounding buildings or on a hill it is more likely to be struck.
If you have say a tall tree nearby, the tree will offer some protection (it will preferentially be struck). Metal on the roof makes little difference (unless it is a "mast") which might be struck. (it causes distortion in the electric field)
Lighning conductors just divert the current to earth. Lighning currents running through damp materials turn the water instantly to steam which bursts open (eg) trees and masonary so causing extensive damage.
Many thousands of amps in a lightning strike, lots of energy.
Many years ago I read that the primary purpose of a lightning conductor was to _prevent_ lightning strikes, by in effect 'short circuiting' the static charge building up in the cloud layer before it gets high enough to arc to earth. Apparently the current passing in a lightning conductor before a lightning flash can be very high, an indication that this shorting process is happening. If the flash actually occurs, it can be interpreted as the lightning conductor having failed to achieve its intended primary purpose.
Having said that, I find it hard to believe that when lightning conductors were first used, short circuiting the cloud was the original intention. They only discovered that much later. I would think the original intention was as you describe, to carry the current to earth down a path that would cause least damage to the adjacent structure.
I doubt it Bob - I heard he'd been struck by lightning.
It takes the path of least resistance, which may or may not be via something high.
If it has sharp corners or spikes these will tend to form leaders and increase the chance of a strike. Twigs on trees can do the same but toa lesser extent. Or the corners may help bleed of the charge and reduce the chance of a strike. Lightning is weird stuff...
Yes, they bleed the induced charge into the atmosphere thus reducing the potential difference and risk of a flash over (strike).
Yep. All bets are off when it comes to lightning, where it will strike and what damage it will do when it does. It's not unknown for the wiring of a house to blown out of the walls as the copper vapourises and anything vaugely electrical to be scrap or there might only be a scorch mark on the brickwork outside and no other damage even to "delecate" electronics attached to long wires (phone lines or WHY).
I don't think its been proven that anything attracts lightening. You can as i have witnessed, have a huge great earthed pylon and the lightening goes via an old tree a few yards away instead.. and makes a bloody racket doing it as well!
Brian
Actually have a look at the mitigation measures taken in Cape Canaveral for deflecting lightening there. T they seem to just use soem avarage looking towers or posts with wires strung between them, and yet things still get hit. No I think its a lot more to do with the conductivity of the air in between one point and another and that is very random and overwhelms the small differences in the size or earthyness of aerials and arrays. I had the highest aerial in the area for many many years and was never struck once, but other houses down the hill from me were so its rather like a lottery, I never won those either. Brian
*Applause*
Does anyone know what happened to him or where he went?. Prolly storm 'chasin out in Texas somewhere;?..
In article , Chris Hogg scribeth thus
Yes this should have been written as prevention of the damage caused by a strike, it doesn't ward them off as such;!..
Yes indeed there is a calculation of that known as the "rolling sphere" method..
Well not that weird, just not that well understood .. some aspects..
There are several anecdotal tales from America where in some states barely a day goes by without out a storm somewhere, sometimes it doesn't even need a storm!, where engineers often tie knots in cables to phones and modems and suchlike they swear that it stops any damaged cased by over volts and spikes.
Seems that the extra "inductance" is helpful to slow such surges!...
Lightning conductors do nothing of the sort. If you actually look at them you will see they have a fusible link just in case they get struck. They actually reduce the chances of being struck not prevent the damage if they are.
The ones at our theatre certainly don't have one and it would have to be yards long to be of any value in stopping a flow of electrons.
Den!, thats not a bloody fusible link its to isolate it so you can test the earth electrode resistance!...
Thank f*ck you confirmed that as I couldn't believe what he had written.
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