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

bg at lysator.liu.se bg at lysator.liu.se
Thu Apr 12 22:38:35 UTC 2012


Said,

The ground is a decent thermal isolator. And will in nordic countries not
often go deeper than about 1 meter. You need to build your houses
foundation "deep" enough to stand on non frozen ground. Otherwise your
house will move to much with the seasons and likely break. It is not that
hard to get your ground pole deep enough to avoid freezing problems.

-- 

   Björn

> 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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