There are at least two whole house protectors that offer protection to all wired utilities that enter the building. Square D's offering can be seen at
Let's see how a transformer can mellow out a surge. Pictures demonstrate how the primary protection system must be inspected and how it can be compromised:
Lightning is not an ideal voltage source. Lightning is a current source. Therefore voltage between transformer primary and secondary will increase until that current flows. IOW voltage will increase until the transformer's breakdown voltage is exceeded. If current has no other path to earth, then current will create a short circuit inside transformer.
Still that internal plasma wire and lightning current does not destroy the transformer. What comes next is more spectacular. Lightning does not have high energy. But electricity from the utility does. Now we have a short circuit from primary voltages (2K, 4K, or 13Kv) to secondary voltages (120, 240). Higher energy electricity from the utility then uses the same plasma connection to literally connect, for a short period, the 2K or 13K voltage into your house. Then the transformer explodes.
Transformer was exploded by energy from a higher energy source - the utility 2K or 13K volt electricity.
Same is true of protection inside the computer. Galvanic isolation provided by transformers inside a power supply can provide 1000 or 2000 volt isolation. These numbers required even by Intel specs. But once that existing protection inside the computer is overwhelmed - once a common mode transient exceeds the 2000 volt breakdown voltage, then internal power supply protection has been compromised.
Yes, a transformer is effective protection when it performs galvanic isolation - acts like a dam. However dams without spillways (the earth ground wire) will fail catastrophically.
Internal appliance protection can be overwhelmed if the typically destructive transient either is not earthed before entering a building (secondary protection), or is not earthed at the pole transformer (primary protection). Once voltage exceeds a transformer's breakdown voltage, then that transformer no longer mellows a surge.
Effective protection is about earthing a transient before that transient can overwhelm protection already inside an appliance. That means earthing so that a transient does not build a plasma wire inside the transformer. Once a transformer's breakdown voltage is exceeded, a transformer no longer mellows. And so we say, protection is only as effective as its earth ground.
"CL (dnoyeB) Gilbert" wrote:
....
So you agree with me then?
I think that most of the posters here are right. Surge protection is best done in layers of protection. It starts with the grounding system, then the entry protectors, all tied to the ground system, then protecting the equipment and all it's inputs to a common grounded point, then protecting any interconnecting paths. Where I live you can't have "too much" protection, but we have about
200 thunderstorms a year and I never unplug anything..
You lost me here. Lightning is electrostatically generated, no current flows until the breakdown voltage of the insulating medium is exceeded. I'm not arguing with you, I'm questioning; what is it that tells you lightning is a current source? I'd call it a voltage source with a high current capacity.
Voltage can only increase as high as the original 'source' voltage. If it were a so called, "current source" the voltage could increase infinitely. But of course this voltage was created due to the flow of electrons which can be considered a current.
Lets not argue about it because it will just get circular. Current source, voltage source is all flakey talk. Its an energy source.
OK. So your calling it a "Current Source", as opposed to a source of current. I don't think its fair to argue about it. Nobody can be right because they both represent ideal concepts which do not exist.
Its debateable whether or not introducing false concepts helps one to understand something. At some point you must understand the truth and let go of the crutch.
Actually, these days the distinction between voltage sources and current sources is quite important in engineering design. I can see how w_tom and others who deal with lightning see the need for the distinction. Some things actually DO work better when you design them for the correct choice of source.
Yes I had voltage and current sources, they were in the basic electricity. I don't see why its easier to say 'current source' than to saw 200MV, but to each his own...
Hmmm, Direct strike? Have you an experience? I was an EIC at a BIG computer systems installation located in a basement of a 7 story building at a university campus. One day we took a direct hit. It knocked off all the substation main breakers(one we have to engage winding up big springs). Garbled data on the mass storage subsystem comprising of ~150 or so hard drives. Now what did you say?
You are replying to a July 2005 thread???
You know, occasionally I see this happen here too. And I've yet to hear an explanation from anybody about how this happens. I'm just curious, as I'm sure others are. Like does it pop up again on some particular newsreader, etc?
Either that, or they are replying through a 'forum' on some web page. Lotsa web sites mirror various Usenet tech groups, to make themselves look more active than they really are. Some of them string-search subjects, and only mirror stuff that looks on-topic for their narrow site. The mirrored posts never get expired. Not all of them are ethical about marking themselves as a web portal on the replies people make. Google your own name some time- your posts will show up on web pages you have never even heard of. Too bad we can't charge those webmasters for our learned words.
-- aem sends...
Tony's a regular here. Maybe he'll say how he ran into the message.
He said direct strikes are easily earthed without damage.
Lightning hit my one-story house. It blew masonry a hundred feet, knocked a hole in the roof, and knocked off siding. It zapped a lot of electronic stuff, including two stereo receivers ten feet from me. Neither was connected to an antenna. One was plugged in but not on. The other wasn't even plugged in.
I was online at the time. My monitor sat blank with blotches of various colors. Cycling it off and on degaussed it. My computer restarted and I found no damage, not even disk corruption. My cordless phone was fine, too.
Across the street, the strike on my house wiped out everything my neighbor had connected to his phone line: computer, satellite receiver, and cordless phone set. For years, he had ignored my advice for simple, cheap grounding to protect him from lightning damage.
Many years ago there was a lightning rod salesman who sold mainly to rural customers. He stopped at a farm and was greeted by a woman who said she didn't want a lightning rod, didn't need a lightning rod, and wasn't the least bit worried about lightning. But, she was afraid of thunder.
At that, the salesman said "You're in luck. I just happen to have a thunder rod in my car!"
He then went to the trunk of his car and pulled out a charred, blackened lightning rod he'd replaced for a customer after lightning struck it.
"Here you are, ma'am, the finest thunder rod available anywhere. I can have it installed for you today!"
The woman bought it, and was so relieved she'd found a thunder rod that she began telling her friends about it, and how she wasn't afraid of thunder any more. They, feeling sorry for her, told the county Sheriff, who quickly tracked down the salesman, forced him to take the thunder rod down, and refund the woman's money.
But from that day forward, the woman was once again a nervous wreck every time there was a storm, and cursed out her friends for helping her.
Hmmm, To late to talk about it but did you install the dish properly to begin with?
Yea, it is too late to talk about it. A second response to a July 2005 thread???
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