[time-nuts] thoughts on lightning arrestors
namichie at gmail.com
Fri Nov 28 03:33:55 EST 2014
Some more thoughts,
It is obvious that lightning strikes do not all have the same intensity. I have not been able to find the statistics
but there must levels of energy that 50% of strikes do not exceed, 90%, ........so a design of
protection probably can never stop extreme strikes. But it makes good sense to stop as many as possible,
and minor protection should stop the small ones, which are probably far more numerous.
Another lightning problem does not concern cloud to ground strikes, but cloud to cloud strikes.
When a cloud has a number of coulombs of charge there is an equal amount of charge on the surface of the ground underneath it, an image charge.
When it jumps to another cloud in a few milliseconds, the charge on the ground underneath attempts to travel to be under the new cloud.
This is seen as massive current spikes, and massive voltage spikes on conductors on the ground, including electrical and transmitting earthing
installations. It will also cause voltage spikes on power lines.
So lightning protection can be quite complicated.
On 28/11/2014, at 5:40 PM, Mark Sims wrote:
> Bark effect? ;-)
> Lightning hit a tree behind where I lived and three other trees near it also exploded... you ain't gonna arrest a direct lightning strike.
> Skin effect did not save the tree.
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