[time-nuts] Thoughts on lightning protection measures....

[Attila Kinali]

Moin,

On Thu, 12 Apr 2012 18:28:24 -0400 (EDT)
SAIDJACK at aol.com wrote:

> if I remember correctly, the issue is that the "ground" at the house is  
> not a "real" ground when the earth is frozen, as the resistance of frozen  
> earth goes up substantially over non-frozen earth. So it's like not having  
> grounded the wires at all.

Yes, that's why in Switzerland you have to bury the grounding loop/wires
at least 1m deep (IIRC), in cold areas even 1.5m deep(again IIRC) to ensure
that the earth never freezes.

I would have assumed that the building rules in the north have similar
requirements, just with deeper digging.

Of course, if you live on permafrost, you will never have a decent ground :-)
  
> This is a real issue for cables brought to the house (cable TV, telephone,  
> etc etc) as those cables are grounded somewhere else on the other side, and 
> thus  there may be 1000's or even 10000's Volts between the two "grounds", 
> even (or  especially) for just a proximity strike. As mentioned by someone 
> else, all bets  are off anyway's for direct hits, not much will survive a 
> direct hit.

Well.. if you have a near hit on some long cable. you're lucky if the
attached electronics survive. But it shouldn't kill everything in the
house. My point was that, with "proper" ground connection, your house
potential should increase to "many 1000s of volt", even with a near hit.
Again, i might miss there something.

>  
> It's been a long time since I designed cable TV receivers, but the specs  
> are here, and I think there are some explanations in there somewhere:
>  
> _http://www.nordig.org/specifications.htm_ 
> (http://www.nordig.org/specifications.htm) 

Thanks, i'll have a look at those.

			Attila Kinali

-- 
The trouble with you, Shev, is you don't say anything until you've saved
up a whole truckload of damned heavy brick arguments and then you dump
them all out and never look at the bleeding body mangled beneath the heap
		-- Tirin, The Dispossessed, U. Le Guin