** Reply to note from "OS/2 Wireless Users Mailing List"
<os2-wireless_users@2rosenthals.com> Thu, 25 Mar 2010 21:48:16 -0400
Serious professional advice from a NARTE certified Master Telecommunications
Engineer since 1985 here about lightning.
> Wow! That's all I can think to say about such a massive lightening strike and
> the negative results. No, that's not true. I think you just convinced me to
> do two things:
>
> 1] Buy a UPS regardless of the physical size of the unit and find room for it
> no matter what! 2] Get myself some renter's insurance, regardless of the
> monthly or yearly premium!
Smart decision. But the folks here need to know some real radio facts about
lightning to make a proper decision on protection. As a commercial broadcast
engineer since even the late 1950's and even Chief Engineer for the Texas Aggie
WTAW radio station back then paying my way through A&M, I offer some serious
information.
Lightning is *NOT* electricity as most people think about that. It is, for
fact, a very intense radio wave issue! As such, it does *NOT* travel through a
wire or metal object! It actually travels on the SURFACE of it. Further, since
it is a radio wave and it oscillates, it also focuses on some frequency during
the actual strike, which CHANGES as the strike takes place in those thousandths
of a second! Frequency means that, as to the stroke going through the
atmosphere or down the surface of a tree, wire; whatever, it has a wavelength
just like a broadcast station transmitter output or TV station. Radio waves are
curious, in that for each QUARTER wavelength we see a MAXIMUM current for
MINIMUM voltage, then a reversal to a MAXIMUM voltage for a MINIMUM current a
quarter wave down the path from there.
The air gap voltage required in the atmosphere for an arc to proceed through it
is perhaps 35,000 or so volts per inch. Think about that. How many million
volts per bolt? Yes, the air is burned into a conduction path, the SURFACE of
which is conducting the lightning. But wait! Remember, a million volts at one
end of the quarter wave point and maybe a thousand amperes current? Then a
quarter wave later a million amperes and then a thousand volts? Interesting.
The absolute 'intent' of a lightning bolt which travels between a cloud and
ground, because it MUST travel on the SURFACE of the conductor, is to actually
spread itself out across the SURFACE of the earth at that end of the path. Well
fine, if as part of the strike conduction path, the surface travel down to the
earth terminates in such a way that on the SURFACE of whatever conductor, that
surface is actually touching and bonded to the surface of the earth. But in the
case of the horrid hit described earlier here, if the metal surface of the
conductor carries it down into a hollow shaft below the surface of the earth,
and thence down the surface of the metal wires to other houses, apartments;
whatever, the only path toward the surface of the earth will be as described.
Through MASSIVE damage sites inside the building(s)!
As well, because the strike is a huge magnetic pulse issue, a strike also
radiates that same Electro Magnetic Pulse (EMP) out away from it. Thus even
though the strike hits your neighbor's house, the pulse lights up EVERY wire in
it's path, at the speed of light, as the energy radiates away from the hit as
well. Interesting.
OK, how do we REALLY protect against lightning? Answers.
That NEMA ground rod at your power meter entrance to the building is there
generically for this reason as well as bonding the power line ground wire to
ground from your electric service. But the real problem is that this NEMA
ground rod is driven INTO the ground! Which does *NOT* do much good for the
radio wave lighting strike which is traveling trying to reach the SURFACE of the
earth. If you really want to use this to protect your home, apartment or
whatever, the proper way to do this is to fan out a little wire radial group in
a circle around that NEMA ground rod, about six or eight feet long for each
wire. Like the spokes on a wagon wheel. Which go down only a small inch or so
at GROUND level from the NEMA rod. What that does is to properly shift the
lightning bolt to the SURFACE of the ground as it roars down the ground wire to
that NEMA ground rod. You do the same thing for the bottoms of TV antenna
poles, metal flag poles, the wire that carries lighting arrester spikes at the
top of the buidling to the ground.
Further, you NEVER pass antenna wires directly into the attic or through the
window into the place - unless - you have a proper lightning arrestor plasma
device which lets the shock arc through it from the SURFACE of the wire that
goes into the building to a good heavy flat sheet copper strip with a wide
surface to the ground. And then out along the surface like the NEMA rod deal.
A round wire has little surface, right? The proper lightning ground is the flat
surface of a copper strip, even though it is rather thin.
Plus the proper place to put the lightning protection on the power, phone lines,
TV cable system and so on is at this common place near your power meter and so
on. That to divert the bolt AWAY from the bulding. You really want it all to
be protected together from a common decent protection set of devices. Even to a
for real master protection set of devices on your meter, and NOT these deals you
buy to 'protect' your stuff in the house. Yes, the do OK for noise. But not
for lightning. About the only thing they are good for is the insurance you may
get with them too. Scowl.
Now we go inside. But before we do please note. OK, so the average quarter
wavelength of the huge bolt is at 1 Megahertz, 1000 Khz on your AM radio dial.
But the bolt also can and does have an average quarter wavelength of only say
EIGHT feet as well with frequencies way up in the TV channel area at points in
it's split second of lifespan. Ouch. Which are still traveling over the
OUTSIDE of all the wires going through your building if you let it in too.
AHA! Now you know why in many strikes that penetrate a building, you'll see
your TV blown to bits on one part of the same power circuit that doesn't fry
your guitar amp eight feet away. Hmmmmmm. More important, there is a HUGE
issue here very few people know and understand about so-called surge protector
plug boxes you get to 'protect' your computer; guitar amp -- and so on. These
protector devices, at least virtually all of them, work by letting a pulse of
over a couple hundred volts arc across a path to the GROUND neutral, the big
round rod on a three prong power plug. Well so what? Remember that because
lightning is a radio wave, just because it shunts the surge to that green wire
ground connection, where is that, in terms of quarter wave spacing, for the hot
spots on the lighting bolt as that happens?
Surprise! Ground, in this case, may not even be back toward the electric panel
and the NEMA rod. Instead, it may be actually going down the SURFACE of that
same green wire INTO your computer, your guitar amplifier, your TV set! Now
watch what else ABSOLUTELY happens to virtually all modern electronic gear.
Years ago we gave up metal transformer power supplies for such things. All of
the conversion from 120 volts or 240 volt of AC (Alternating Current) down the
power lines to the DC (Direct Current) for the equipment, is done through what
is now switching power supplies. But that is a DISASTER for a voltage spike
which comes IN on the green ground wire, seeking out the phone line ground,
perhaps, or .. worse .. your PRINTER! Because your laser printer draws a high
power amount you can't pay for UPS coverage. So you plug it in to the power
plug and then connect it with a metal ground wire to your computer which is on
your UPS. Get the idea?
What happens is that the lightning strike, even only a hundred volts maybe by
the time it gets here, raises the GROUND foils of your computer above the GROUND
level for a SURFACE radio wave for the difference of 120 volts AC to 12 volts DC
and... Surprise! If it is a 300 volt pulse, your ground foils are 30 volts
above ground and POOF your whole computer, guitar amp, TV set, stereo is blown
to bits. It is not at all unusual for even a strike on your neighbor's place to
surge your power lines up to 600 volts or so. Not at all.
Bottom line. The ONLY way to use a UPS to protect anything is to make SURE that
your UPS uses a METAL TRANSFORMER to isolate the house from whatever you are
trying to protect. Why? Because the lightning bolt cannot pass through the
metal pig iron between the primary coil and the secondary coil wires in it.
Thus that really DOES ISOLATE your equipment from the pulse. But ONLY if you
protect ALL of the devices on the output side. And do *NOT* run your printer
elsewhere and then connect it to your computer. Or use any kind of phone line
or cable modem connection metal wire to another ground possible source to the
protected device. Without thinking carefully how it is absolutely protected to
keep the pulse out of the building and shunted to ground properly.
There does happen to be a form of surge protector that does not have this
horrible pulse clamp effect. But it is quite rare. It uses an inductor choke
and capacitor to clamp the pulse to the HOUSE side of the power line service and
like the transformer style device, blocks the pulse from crawling on the surface
of the wire into your equipment. It sure isn't sold in Walmart, Lowes, HEB or
any place like that folks.
Final notes here. If you are using huge antenna farm stuff like I do as a
serious ham radio operator with towers all over the place at my site, you also
may be required to put a substantial metal wire circular ring around the house
which bonds the various sink ground spoke sites at several places going into the
building! And, in fact, my site gets a direct hit on the average of at least
twice a year big time. My towers are all grounded and radial spanned at the
bottoms for protection purposes. As well the feed lines are all brought in
either at underground level, properly protected by plasma arc protectors there
at tower connections. Or in the proper ground plate side panel entry points
that do properly connect to the ground. I have had this careful protection
since about 1980 at the site. And direct hit after direct hit, I have NEVER
since ever had a computer failure or radio or any failure, other than a couple
modem failures ever since properly protecting it.
But I do use all proper pig iron UPS stuff there. Which in my case has been for
years the APC full professional sine wave output Smart UPS units. As well all
the computer equipment on the site is also actually still pig iron linear power
supply relay rack stuff. I use *NO* switching power supply stuff at all in any
rural heavy tower radio site locations, like we also never do at broadcast
stations. Which get hit a heck of a lot more with their 250-500 foot high
towers that are a lot higher than mine, chuckle. And at WTAW's 1150KHz AM
frequency is a 256 foot quarter wave high tower. Which we took about 60 hits a
year while I was Chief Engineer there paying my way through A&M. And never once
lost anything from an antenna strike.
Sorry for all the words. I am just trying to help here..
> Do you have any quick methods of how-to size up what power-level of UPS to
> buy? I know I can go to google.com and find the info but if you have some
> quick method off the top of your head it will save me the time of reading and
> figuring out for myself what I need. Not to mention the fact that also I
> trust your judgment more so than what I might find on the 'net.
You have to totalize the wattage level use of the electronic equipment you wish
to protect. Then you figure out how long the batteries of the UPS will crank
out that much wattage to keep things going. Either so you can shut it down if
you are hit, or it will go on until the real chances are that decent power will
be restored. At my ham radio site, when I am not there, the APC UPS with the
battery power level available to it, will keep the simple computer, phone line
access and low level VHF data service going for about 24 hours. I've only once
since the 1980's ever not been able to get out there in more than 24 hours to
shut things down and police the things if I'm not there on site when bad things
happen to the power at this very rural location.
Not the same Mike.
> Thanks Mike, seriously! You've knocked some digital sense into this old
> brain-pan of mine, and for that I am grateful. I'd be sick if I lost even
> half of my gear!
>
> Greg
But with the best of my professional heart at work here to help not only you but
the otheres who might benefit from this.
--> Sleep well; OS2's still awake! ;)
Mike Luther
Mike.Luther@ziplog.com
Mike.Luther@f3001.n117.z1.fidonet.org
Nazaj na seznam