Lightning conductors

[Owain]

"Andy Wade" wrote | The conductor(s) can carry strike current easily. The danger, and | damage, come when the current leaves the conductor and forms an arc | - in a 'side flash'. The peak power in the arc can reach 100 MW/m, | heating the surrounding air to 30,000 K and initiating a shock wave. | It's the shock wave that blows tiles off roofs, etc ... | Finally the earth system design is not trivial. BS 6551 requires an | earth system resistance not exceeding 10 ohms. 200 kA through 10 | ohms will drop 2 MV, so voltage gradients at the ground surface | (between someone's feet, for example) become an important consideration...

Memo to self: Do not pee against a church tower during a thunderstorm.

Owain

[nightjar]

If a lightning conductor is struck, it has failed in its main purpose. What it is supposed to do is to cause a gradual discharge of the potential difference between earth and cloud, thus preventing a high enough charge from building up to create a strike. A proper installation has a number of air terminals, to create a brush discharge effect, and numerous conductors, to distribute the load across as wide an area as possible. While copper tape is widely used, some engineers prefer iron, because it has a higher impedance.

Colin Bignell

[stefek.zaba]

I believe so - memory augmented by Google suggests both Ayrshire and Dumfries. Presumably they put the plants in areas of relatively low population density ;-)

Always seemed a touch amusing to have the Nobel Peace Prize instituted to assuage old Alfred's guilt at inventing TNT, while ICI (which I believe bought up his business interests) kept the name going with the more original association!

Stefek (son of an ICI engineer)

[Andy Dingley]

And also because of the skin effect. The current flow isn't using the centre of that strip, even at a mere 1/8" thick.

-- Die Gotterspammerung - Junkmail of the Gods

[Andy Wade]

True.

[Mungo Henning]

The Stevenston ICI site (Ayrshire) is concerned with explosives manufacture. Dunno if that's its sole output though. This ICI explosives site is built on the coast with lots of sand dunes surrounding it (the folklore being that with sand surrounding it German bombs were less likely to explode when dropped onto sand during World War two).

Mungo

[DKSanders]

Thanks to you all for the very informative and interesting responses.

I had no idea there was so much involved or to be considered. Therefore I will use from stores: a No 1, Pole, Barge, Avoidance, for the use of. and recommend that my friend contacts e.g. Furse if he is really sure he needs one.

Thanks again all, I was very impressed by the level of knowledge out there and found it fascinating reading.

Dave

[tony sayer]

In article , DKSanders writes

Wimp! One small flash-bang-wallop!!.........

Seriously I suggest that you have a butchers in the Yellow pages. If you haven't anyone out your way then there is a firm W.Gray of somewhere in the Essex area who do travel over quite a wide area, but I still reckon that its not going to be cheap.

Perhaps you mate might like to DIY himself!..

[DKSanders]

Thanks Tony,

Wimp, maybe.. but at least a non-fried wimp :)

My mate couldn't change a torch battery safely so this is sci fi league to him. He's checking with the architect who drew up the plans if he really needs a conductor, I'll pass the info on in case he does.

Thanks again.

Dave