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

[Chuck Harris]

Hi Bob,

When I had my lightning protection survey done on my house,
there was a requirement that all of the lightning grounds
be tied to the power, telephone, cable, and water grounds
at a single point.  Before I did this, I lost modems, network
cards, fax machines, etc.. afterward, no problems.

I do lose the occasional phone surge protector in the network
interface block, but they seem to do their job, and protect
everything else.

-Chuck Harris (knocking on wood!)

Bob Camp wrote:
> Hi
>
> Yes indeed, very true.
>
> Things like telephone lines and cable lines need to "jump" at the same time
> as the house ground. The fact that they don't is what makes cordless phone
> base stations, modems (remember them?) and cable boxes the main victims in
> lightning hits.
>
> Bob
>
> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
> Behalf Of Chuck Harris
> Sent: Friday, April 13, 2012 9:14 AM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] Thoughts on lightning protection measures....
>
> As the power line worker strapped to the million volt wires he is
> working on shows, what is important is that all the grounds in the
> house stay at the same potential... not that they stay at some
> perfect earth ground potential.
>
> It really doesn't matter if a "house" ground jumps up many
> thousands of volts for an instant during a lightning strike, as
> long as everything electronic in the house, and everything
> structural in the house jumps too.
>
> -Chuck Harris
>
>
> Attila Kinali wrote:
>> 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
>>
>
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