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Posted by w_tom on October 19, 2007, 2:35 pm
> That's a common misconception, based on the average 30,000 amp
> estimate of a lightning strike and trying to figure wire size.
> But it's not a steady state current. It's a sharply dampled sinusoid,
> and #10 wire is more than adequate for any expected strike.
TimR has accurately defined why so little wire can conduct such
massive surges. Electrical Engineering Times has two articles
entitled "Protecting Electrical Devices from Lightning Transients" at:
http://www.planetanalog.com/showArticle.jhtml?articleID=201807127
http://www.planetanalog.com/showArticle.jhtml?articleID=201807830
This discussion is based in engineering principles and with
numbers. Notice how much current is carried by an 18 gauge wire? If
I remember, 61,000 amps. Wires used for AC power would have maybe
four times that capacity.
BTW, also notice everything defined for surge protection. Notice
the article never discusses plug-in protectors or a UPS. This
professional engineering trade rag is not selling hype and myth. Both
articles discuss the only thing required for surge protection -
earthing and connections to earthing.
What is a protector? A connecting device to earth ground. It must
*divert* a surge to earth. But earth ground defines that protection.
This engineer author discusses wire size to conduct lightning to
earth, how wires must be routed, why that connection must be so short,
AND of course the most important part of surge protection - the earth
ground electrode. Protection of electronics is defined by the most
critical component in any surge protection system - earth ground.
This engineering article on lightning protection discusses what most
important component? Earthing.
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Posted by w_tom on October 20, 2007, 1:33 am
> That's a common misconception, based on the average 30,000 amp
> estimate of a lightning strike and trying to figure wire size.
> But it's not a steady state current. It's a sharply dampled sinusoid,
> and #10 wire is more than adequate for any expected strike.
TimR has accurately defined why so little wire can conduct such
massive surges. Electrical Engineering Times has two articles
entitled "Protecting Electrical Devices from Lightning Transients" at:
http://www.planetanalog.com/showArticle.jhtml?articleID=201807127
http://www.planetanalog.com/showArticle.jhtml?articleID=201807830
This discussion is based in engineering principles and with
numbers. Notice how much current is carried by an 18 gauge wire? If
I remember, 61,000 amps. Wires used for AC power would have maybe
four times that capacity.
BTW, also notice everything defined for surge protection. Notice
the article never discusses plug-in protectors or a UPS. This
professional engineering trade rag is not selling hype and myth. Both
articles discuss the only thing required for surge protection -
earthing and connections to earthing.
What is a protector? A connecting device to earth ground. It must
*divert* a surge to earth. But earth ground defines that protection.
This engineer author discusses wire size to conduct lightning to
earth, how wires must be routed, why that connection must be so short,
AND of course the most important part of surge protection - the earth
ground electrode. Protection of electronics is defined by the most
critical component in any surge protection system - earth ground.
This engineering article on lightning protection discusses what most
important component? Earthing.
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Posted by on October 9, 2007, 8:08 pm
>30 years ago lighting struck the building across the street from my office
>and destroyed one of the 9 computer monitors in my office. That is the only
>damage I have ever seen from lighting, despite never unplugging anything. I
>am wondering just why she is unplugging everything. (I expect it did a bit
>more damage in the building it hit; it is also the only lighting strike I
>have ever seen hit.)
I am in SW Florida where we have flash/bang ligntning all the time
(hit so close the flash and bang are together). I never unboplug
anything.The only thing I have ever lost was my weather station and it
"almost" worked. (RF was fine, wired connection failed) The lightning
hit the air terminal on the post the wind speed indicator was on.
I have PCs networked all over the house and one in the garage.
The trick is good lightning protection and a good grounding system
that everything connects to. You need protectors on everything coming
in (Power, Phone and Cable). I also have point of use protection. The
hole in my system was that wire from the wind sensor but the damage
was still isolated to that one box. The PC it plugged into was fine. I
now have that on a protector too.
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Posted by Terry on October 9, 2007, 8:23 pm
>>
>> In the last sixty years, I've unplugged many an AC cord, but I've
>> yet to 'leave parts of the plug' in the outlet! I hope you mean by
>> 'pulling it out of the wall', you aren't pulling on the AC cord itself?
>> Rather than grasping the plug near the outlet and gently but firmly
>> unplugging it?
>>
>> Just wondering.
>>
>I was wondering about that also, I have never heard of anything breaking off
>in the outlet!
>
It sure does sound like the OP is pulling the cord and not the plug.
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Posted by chicagofan on October 15, 2007, 6:30 pm
Terry wrote:
>
>>> In the last sixty years, I've unplugged many an AC cord, but I've
>>> yet to 'leave parts of the plug' in the outlet! I hope you mean by
>>> 'pulling it out of the wall', you aren't pulling on the AC cord itself?
>>> Rather than grasping the plug near the outlet and gently but firmly
>>> unplugging it?
>>>
>>> Just wondering.
>>>
>> I was wondering about that also, I have never heard of anything breaking off
>> in the outlet!
>>
> It sure does sound like the OP is pulling the cord and not the plug.
LOL... creeping senility is a problem, but that's one thing I haven't
done. The prong of the left side of 2 plugs now, have been left in the
wall outlet... pulling on the plug normally.
bj
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Page 6 of 6 << first < 1 2 3
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