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

SAIDJACK at aol.com SAIDJACK at aol.com
Thu Apr 12 22:28:24 UTC 2012


Hi Attila,
 
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.
 
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.
 
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) 
 
bye,
Said
 
 
 
 
In a message dated 4/12/2012 09:54:40 Pacific Daylight Time,  
attila at kinali.ch writes:

Hmm?  That sounds interesting. In switzerland, and AFAIK in most  european
countries, power feeds have to be grounded at the entry of the  house
(ie the neutral conductor is grounded). This should protect the  electrical
equipment from such ground jumps as you discribe. Or do i miss  something?

Attila  Kinali




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