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

[Bob Camp]

Hi

The process of bonding everything together is a lot easier if the house is set up with all the "stuff" coming in at one point. If phone, water, power, and cable all come in on their own corner - not quite so easy.

Bob

On Apr 13, 2012, at 5:34 PM, Chuck Harris wrote:

> 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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