[muglo] Re: [muglo] Re: Storm Protection— A mini course in electricity re UPS protection from lightning
- From: SPELL BOUND PUBLISHING <spellboundpub@xxxxxxxxxx>
- To: muglo@xxxxxxxxxxxxx
- Date: Mon, 14 Jun 2004 20:56:38 -0400
An uninterruptible power supply (UPS) is a great idea, for anyone=20
operating a computer or any other sensitive electronic device.
Besides handling electrical spikes (high voltage surges caused by heavy=20=
motors switching, power surges from your local power company or other=20
sudden loading or unloading of the power network, such as lightning=20
strikes that open circuit breakers, etc.) they can also protect your=20
computer and data from brownouts (typically, where the voltage sags due=20=
to loading of the power network beyond what it can generate).
Because Macs use switching power supplies, which adjust dynamically to=20=
the voltage at your wall plug, they can adapt to a wide variety of=20
power variations. The UPS is of importance when the wall plug voltages=20=
reach extreme values. Today's UPS's are intelligent devices that can be=20=
set up to shut off your computer without your intervention. This is=20
handy if there is a lengthy power outage and you are not at your=20
computer.
Because of the nature of our power system, there are always brownouts=20
and spikes occurring. If you already own a UPS, then you will already=20
be aware how often brownouts occur, since most UPS systems will beep=20
when they switch over to their battery supply, even if it is only for a=20=
number of milli-seconds. The spikes are filtered quite simply by=20
solid-state electronic components that channel any high-voltage spike=20
directly to ground, by-passing all of the essential circuitry.
Lightning, of course, produces some very different effects, depending=20
on whether your building is being supplied from overhead wiring (on=20
power/phone poles), or underground wiring (from near-by transformers=20
on/under the ground).
OVERHEAD WIRING: Since lightning can produce many millions of volts,=20
these strikes can produce devastating results. These results will=20
typically be worse, if your building is being fed by overhead wiring.=20
Overhead wiring can carry a lightning-generated spike directly to your=20=
building, from quite a distance, since there is little to obstruct its=20=
travel. There may be sites between you and the lightning strike where=20
the voltage can arc to ground, and lose some of it's intensity.=20
Distance from the strike plays a big factor in the intensity as it=20
arrives at your computer.
UNDERGROUND TRANSFORMERS are quite a different story. Both the primary=20=
and secondary circuits run underground and are somewhat protected from=20=
lightning strikes. Primary circuits eventually lead back to a pole, but=20=
the secondary circuits go straight to your building and are always=20
underground, except where they exit to supply the circuits in your=20
building. The primary side is fed by high voltage (7000+ volts,=20
depending on the system). The secondary side is connected to your=20
building and typically includes dual 120 volt circuits, which can=20
combine to produce 240 volts for devices like your electric stove,=20
clothes dryer, etc.. Both 120 volt circuits will be used to supply the=20=
alternate wall plugs in your building.
The secondary circuits have an insulation that can withstand somewhere=20=
between 12,000-25,000 volts before the voltage will punch through the=20
insulation and arc to ground. Since lightning is such a high voltage,=20
underground wiring insulation will normally fail and short out most of=20=
the lightning energy before it reaches your building and your computer.=20=
Thus, the underground service will provide more protection from=20
lightning strikes, than the overhead service will.
DIRECT OR NEAR BY STRIKES can have totally different results. There are=20=
electric and magnetic fields associated with the static voltage that=20
creates the lightning and the current flow (of course, once the=20
lightning arcs, a current flows and it is no longer static). Large=20
time-varying magnetic fields can induce voltages (and thus secondary=20
currents) in wires or circuits that are nearby. They can cause large=20
currents to flow in devices that are "turned off" or "unplugged". Any=20
part of a circuit that forms a loop, can have this current flow, even=20
when not connected to any power supply, or battery. Since today's=20
components have components and wires that are so tiny, it doesn't take=20=
a lot of induced voltage to overload the micro-circuitry and damage it.=20=
A similar event can occur strictly from the static electricity=20
component of a lightning strike.
The UPS can effectively protect your equipment from the more distant=20
strikes, but probably will not be able to protect you with certainty,=20
from a direct or near-by strike. Most likely, any strike close enough=20
to cause the induced effects, will probably destroy the UPS and=20
possibly your equipment. The up-side=97if there is one=97 is that most =
UPS=20
companies insure YOUR equipment to $25,000, for example, if it is=20
destroyed while plugged into THEIR UPS. So that's a good reason to=20
install a UPS and another good reason to REGULARLY back up your data.
Hope this isn't too technical... but it might give you a better=20
understanding what you can expect from a UPS. I personally think they=20
are worth every penny=85 and they are so inexpensive today, compared to=20=
when I purchased my first two, about eight years ago.
Larry
On Saturday, June 12, 2004, at 11:24 AM, Ilbert Walker wrote:
> Here's my answer, friends. Expensive, but it lets me sleep at night =
!
> After last year's fiasco of brownouts etc - I decided that the $ cost
> of fried Macs, and lost info without backup was insignificant in
> comparison with my time in trying to recoup everything. Tempus fugit
> for me !!
>
> I wanted to leave my G5 on 24/7 whether in or out of my dwelling - and
> not having to arise for middle of the night storms!
>
> After much investigation and help from Peter Miazga, I bought an APC =
C5
> BackUp unit (expensive!) which automatically shuts my Mac down, after =
a
> preset save time, with or without my physical presence.
>
> Power bars etc are ok for a limited (and not inexpensive) solution, =
but
> I sought a more sophisticated, fail-safe system. It's operated okay
> now for 9 months through all sorts of storms and brown outs.
>
> We have to face the fact that we do live in 'tornado alley ' here in
> SWO, plus connection with the US powergrid :-)
>
> My 2 cents worth ( well not quite that !! )
>
> Ilbert
>
>
>
> On 12 Jun 2004, at 9:40 AM, N. Barry Alexander wrote:
>
>> I also had my iMac fried once in a thunderstorm. So, if there is a
>> storm
>> nearby, I unplug everything just to be safe. I'm sure the powerbar=20
>> with
>> surge protection work, but I'm not sure if I'm going to trust it.
>> Better
>> safe than sorry.
>>
>> Barry A.
>>
>>
>>
>>
>> On 6/12/04 8:45 AM, "Marty Peterson" <marty.peterson@xxxxxxxxxxxx>
>> wrote:
>>
>>> I have held a bad experience with my MAC plugged into a wall outlet.
>>> In
>>> September 2002, I had plugged my MAC into the wall, the same outlet
>>> as the
>>> answering machine. Through the night we had a terrible thunder =
storm
>>> that
>>> hit the house or close to it. The answer machine was fried but the
>>> compute=3D
>>> r
>>> seemed fine. Over the next couple of weeks the computer began to
>>> become
>>> slower and slower. Thinking the problem was a lack of RAM, I order
>>> more fo=3D
>>> r
>>> it. (PowerBook G3 with standard 64mb). Six or seven pieces of RAM
>>> later we
>>> discovered that it was damaged by a power surge from the lighting.
>>> This of
>>> course meant replacing the computer totally and I now have a G4
>>> PowerBook
>>> that I immediately unplug it from everything during a storm and
>>> continue to
>>> work on battery.=3D20
>>>
>>> Marty
>>>
>>>
>>> On 6/12/04 8:29 AM, "Theresa Roth" <theresaroth@xxxxxxxxxxxx> wrote:
>>>
>>>>> With all the storms that we have had recently - and who knows for
>>>>> the
>>>>> future!! - is it necessary to turn off the power, unplug the =
supply
>>>>> and/or disconnect the telephone line to the modem? It seems these
>>>>> days
>>>>> that people leave their computers on in storms!! Perhaps they are
>>>>> more
>>>>> robust now?
>>>>> =3D20
>>>>> Paul
>>>>> =3D20
>>>>> _________________________________________________
>>>>> =3D20
>>>>> =3D20
>>>> I left mine on as I=3DB9ve never had a problem. I do have a $35
>>>> powerbar whi=3D
>>> ch
>>>> I=3DB9m not sure if it=3DB9s also a surge protector. Here=3DB9s =
what
>>>> happened: My
>>>> o=3D
>>> ld
>>>> TV got cooked (straight horizontal line), my water heater fried, my
>>>> furna=3D
>>> ce
>>>> merely shut off, a cordless phone fried and I was without phone
>>>> service f=3D
>>> or
>>>> 48 hours. My Mac is ok but the phone jacks in the powerbar are
>>>> fried. I
>>>> assume the powerbar protected my Mac from surges both through the
>>>> electri=3D
>>> cal
>>>> and phone lines. But now, I can=3DB9t use the phone jacks in the
>>>> powerbar an=3D
>>> d
>>>> must plug the Mac into the wall directly. I=3DB9m unsure of =
whether
>>>> this wil=3D
>>> l
>>>> prevent surges and/or damages in the future.
>>>> =3D20
>>>> Theresa
>>>> =3D20
>>>> _________________________________________________
>>>> =3D20
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>>>> =3D20
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>>>> =3D20
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>>>> =3D20
>>>
>>>
>>> _________________________________________________
>>>
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>>>
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>>>
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>>>
>>
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>>
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>
>
> _________________________________________________
>
> For information concerning the MUGLO List just click on
>
> http://muglo.on.ca/Pages/joinus.html
>
> Don't forget to periodically check our web site at:
>
> http://muglo.on.ca/
>
>
**********************************************************
Larry Kryski
Spell Bound Publishing
London, Ontario N6L 1E3
Canada
Ph: 519 652-8267
Fx: 519 652-8268
e-mail: spellboundpub@xxxxxxxxxx
WWW: http://members.rogers.com/spellboundpub/
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