# Is it safe to use computer during lightning/thunder storm?

Discussion in 'Electronic Basics' started by nospam256K, Sep 21, 2004.

1. ### Roger JohanssonGuest

I can take up one more point. The ideas you express above are simply
wrong, there is no scientific basis for that.

In fact, it is often a component close to the input connection which
fails, because the charge that comes rolling down the wire uses the first
possibility to unload itself to a potential closer to earth level.

2. ### Ron ReaughGuest

Clueless. This wacko has been stalkin large numbers of NGs for many years

A well know fact is that good surge protection of electronic equipment has
little to do with the earth ground. Just ask yourself how things are
protected on an in-flight airplane. That technology is what is involved in
good protection. When you are on the ground then providing a safe place for
that lightning bolt to find earth ground is a real good idea for safety
reasons but that has little to do with protecting electronic equipment like
computers. Protecting such equpiment depends entirely upon shunting any
overvoltages to common mode and the chassis.

3. ### P.T. BreuerGuest

Mmm. Very reasonable. Good explanation.
Peter

4. ### Ron ReaughGuest

You see there really are people around who understand surge protection.

5. ### w_tomGuest

Electricity flows like an ocean wave? Now I know you have
absolutely no engineering knowledge. First electricity forms
a complete path from cloud to earth. Then as the current
increases within everything in that circuit, then something
eventually fails. Without the complete circuit, there can be
no electricity flow. That means first electricity flows
through everything in that circuit. Later something in that
circuit fail. Typically the entire surge is done in
microseconds. But the component can even take milliseconds to
fail. Electricity does not flow through devices like an ocean
wave - except where myths are promoted.

A simple principle is taught in Electromagnetic wave theory
- something taught to second year engineering students. Apply
electricity to a long wire. Where does voltage first appear?
Those who think of electricity in terms of ocean waves would
say voltage first appears where electricity connects to that
wire. They would be wrong because they did not learn
basic electrical principles. Instead, voltage first appears
at the far end of a wire. Again, a simple principle taught in
wave theory.

You are absolutely wrong that the charge, rolling down the
wire like an ocean wave, uses the first possibility to unload
itself. Wild speculation based upon junk science reasoning -
that electricity flows like ocean waves.

Classic modem damage is a circuit from cloud to earth. Only
after current flows through everything in that circuit, does
component failure occur. The component most often damaged by
an AC mains surge is in the DAA section - where phone wire
carries the current out of the modem to earth ground.

And again, if a surge is incoming on phone line, then why
does the always present phone line protector - installed free
by the telco - get ignored by the surge? Only if Roger did
not know the protector exists. Please explain why surges would
enter on a utility wire with 'whole house' protector AND not
enter on the utility wire that has no protector? Why would a
surge be created on a wire both lower and protected by the AC
mains wire? Clearly the incoming surge comes from the wire
highest on pole AND via wire that has no 'whole house'
protector - AC electric. Clearly, you do not even know that
phone line protector exists.

Furthermore, you are inventing new ideas on how electricity
works. Clearly you have no engineering training. Therefore
you are attacking my experience and credibility so that others
will be confused. You have no idea how electricity works.
Posting as if your entire electrical knowledge was in swapping
computer boards or because you sell consumer electronics with
highly profitable plug-in protectors. Again, where on that
long wire does a voltage first appear? At the end connected
to an electricity source (just like an ocean wave)? Or at the
far end of the wire. It is electricity - not an ocean wave.
Where does the voltage first appear?

Since voltage first appears at the far end of a wire, then
your wild speculation about what component is first damaged is
bogus. You believe the first component damaged is "a
component close to the input connection". That assumes
voltage first appears at the input connection. It does not.
According to your reasoning, the first component to be damaged
due to "power unloading itself" would be the *last*
component. The last component in that circuit would be the
first to see voltage from a surge using your reasoning.
Please do not invent electric concepts in a vacuum. Please
first learn how electricity works. Electricity first flows
through everything in that circuit. Only then does something
fail.

You are having difficulty even with concepts taught to first
year engineering students. That would explain why you hope a
plug-in protector is doing even what the manufacturer will not
claim. Its really a simple principle. A surge protector is
only as effective as its earth ground - which also explains
why the modem surge does not enter on phone line.

The original poster is encourages to place a 'whole house'
protector on the one utility that typically has no surge
protection - AC electric. Other wires such as phone line and
cable should already have protection, in part, because those
connections are required by National Electrical Code - for
other technical reasons.

6. ### w_tomGuest

Effective protection is not possible by unplugging. First,
you are not available even one third of the day. Most of the
time is spent sleeping or out working, etc. Second, many of
those appliances cannot be always unplugged - ie answering
machine, phone, and that TV. Having spent many decades
learning this stuff, I now have equipment on during
thunderstorms - often following the storm in real time. No
damage because money was not wasted on grossly overpriced
protectors recommended by urban myth purveyors. Provided is
both the superior protection method AND the less expensive
method. It is called 'whole house' protector. So effective
that the phone company installs one for free in your phone
line premise interface.

Wires most often struck are wires highest on the pole. These
wires make a direct connection to every household appliance
without any earthed 'whole house' protector. Earthing the
direct strike is essential to protection. One minimally
acceptable 'whole house' protector is sold in Home Depot as
Intermatic IG1240RC. Many other responsible manufacturers
such as Leviton, Square D, Cutler Hammer, Erico, Polyphaser,
Furse, etc all sell these products. But still we have people
foolishly recommending plug-in protectors. When challenged,
we discover they have no basic electrical knowledge - which
explains why they did not even know the phone line protector
already exists. Then when those plug-in protectors fail, they
say nothing can protect from lightning - and recommend more of
those ineffective protectors.

One can never unplug for effective protection. The human is
not reliable enough nor available 24/7. But 'whole house'
protectors connected 'less than 10 feet' to earth ground are
that reliable.

Rich, you had to rearrange transistor leads because Japanese
use ECB configuration verses an American EBC configuration?

7. ### w_tomGuest

Roger - chances are I was experimenting with this stuff
before you existed. It is quite likely that I had my first
engineering degree before you were walking. Polyphaser
equipment was defined for someone who does not even have first
year engineering education. Earthing a surge must be
accomplished with very short wire - as close to the single
point earth ground as is possible. And so the Polyphaser
device mounts directly ON earth ground. That distance being
that critical to effective surge protection.

Yes we cannot make a perfectly conducting earth ground. So
we also make the earth beneath a building equipotential. We
enhance earth ground using Ufer grounds and halo grounds. But
again, such conductors are not perfect. Even with a metallic
earth ground, we still do not have equipotentail. Therefore
we attempt to ground everything in the building to a the best
conductive single point ground. We conduct the surge aways
from the building as best we can. And we make the building
and its underlying earth a short of faraday shield. These are
compromises. But together, they are sufficient to avoid surge
damage. It is why we best put the surge protector directly ON
the single point earth ground. Shorter connection to earth
ground means the protector is more effective. Again, a
protector is only as effective as its earth ground.

All this is well beyond the original poster's question. But
it explains why he wants a 'whole house' protector and why
plug-in protectors don't create these protective equipotential
shells as was advocated.

Obvously if a power strip protector if not earthed, then it
leaves adjacent electronics at thousands of volts with many
other and destructive outgoing paths. Nothing in a room can
remain at thousands of volts in isolation. If the computer
and power strip rise to 13,000 volts, then that voltage will
create other destructive paths to earth ground (see next
paragraph). Again, a power strip manufacturer claims only
normal mode protection. Plug-in protectors cannot provide
effective protection because they are too far from earth
ground - effectively not earthed. No earthing means no
effective protection.

To be effective, the single point ground must be building
wide because building interiors are chock full of 'surprise'
conductive paths. For example, conductive paths include
linoleum tile and some wall paints. These too must be
connected to a power strip surge protector for that protector
to be effective. They are not. If the power strip and
computer rise a few thousand volts during the surge, then that
voltage finds a destructive path to earth ground via mouse
cable where cable contacts wall paint or baseboard heat. The
power strip protector concept, as advocated, only works if the
entire room was constructed, in advance, to be a farady cage.
Neither the orignial poster nor others here have room
constructed that carefully.

Even in high reliablity facilities such as telephone
switching centers, cell phone towers, and commercial broadcast
centers, we install effective 'whole house' protection. The
simplest, least expensive, and most effective way to protect
household electronics is also the 'whole house' protector with
a single point earth ground as required by post 1990 National
Electrical Code requirements. Then the entire building rises
and falls equipotentially during a surge. Again, we want the
protector short to earth ground and farther from the protected
electronics for two reasons. We want the surge conducted to
earth using the most conductive path. And we want the entire
building to rise and fall equipotentially.

Furthermore that 50 foot of 12 AWG AC wire inside wall
contributes to computer protection if we use a 'whole house'
protector. Using a plug-in protector, then that 12 AWG wire
instead contributes to computer surge damage. So many reasons
why the less expensive 'whole house' protector is also so much
more effective.

Spend \$15 or \$50 to protect each appliance in the building.
Or spend about \$1 per protected appliance for a 'whole house'
protector - that actually does what that power strip can only
hope to accomplish. The 'whole house' protector does that
task at tens of times less money AND can protect everything.
Even if the power strip protector protects a computer, it
leaves everything else in the building exposed. Why spend so
money on a device that 1) does not even claim to protect from
all types of surges and 2) costs tens of times more money per
protected appliance?

A surge protector is only as effective as its earth ground
which is why a properly protected facility installs 'whole
house' type protectors. More protection. Less money.
Includes the essential 'less than 10 foot' connection to earth
ground.

Anything that a power strip protector will accomplish is
already inside those appliances. But those appliances assume
the destructive surge will be earthed before entering a
building. Technology well understood even before WWII. These
plug-in protectors must have us ignore earth ground to make
the sale. No earth ground means no effective protection.
Again, I may have been doing engineering longer than you have
existed.

8. ### w_tomGuest

IOW the giant electrical wave appears just about equally on
everything in the circuit. That is your delta wave.
Virtually everything is located in the same part of the wave
meaning there is near zero voltage difference.

Surges are done in microseconds. Things go bang in
milliseconds. How do you explain the discrepancy? Its quite
simple. Damage occurs to the circuit component that is
weakest and that absorbs excessive power. But that means
everything is exposed to the current equally. Correct.
Everything is exposed to the same circuit. How do we know?
The surge is done in microseconds. The damage (ie a fuse
blows) in milliseconds.

He is quite silly to claim electricity flows like a wave as
are you. Your claim that electricity appears like an ocean
wave denies basic EM theory. Where does the voltage first
appear? At the far end of the wire.

Well this three reasons why it is silly to think the first
component always fails. Are you also an electronic appliance
salesman? How do you explain the contradiction between wave
theory and your claims? How do you explain the time
difference between a surge and when the damage physically
appears?

Moving on - since phone lines already have effective 'whole
house' protectors AND if the first electrical component
encountered is the first one damaged, then why is the first
damaged component on the phone wire side. How, pray tell,
does the surge ignore a properly earthed surge protector to
enter modem on phone line side? And why does the wire highest
on pole - wire that enters building without an earthed 'whole
house' protector - not carry the surge into a modem. How is
the first component in modem damaged when the surge cannot
even enter from that direction?

Please explain how a surge routinely bypass AC electric
wires to strike phone wires AND then completely ignore the
telco provided 'whole house' protector. This is only possible
if we reinvent electricity to meet our fictions.

Don't be so foolish. Electricity first flows through
everything in the circuit. Only then does something fail.
Everywhere except in science fiction.

9. ### P.T. BreuerGuest

Don't be silly. His point is that anything close to the entry (and
exit) point is a winner in the low resistivity stakes. Anything further
away will see a lower EMF, since current is flowing through the
conductors that supply that emf. So the closest things are likely to go
bang first. When they have gone bang, the next thing along might also
go bang.

And yes, electricity DOES flow like a wave. It's called the delta
response curve (in a circuit with parallel capacitance and serial
resistance). And a lightning strike is a big delta.
!!

Peter

10. ### P.T. BreuerGuest

Never heard of it, and I have my PhD in electrical engineering from U.
Cam. Oh well.
He doesn't care, and neither do we, since as he pointed out, the
equipment doesn't care if it's earthed or not! That's why airplanes
keep right on flying when hit by all that electrickery ...

Peter

11. ### P.T. BreuerGuest

Sure it does, at different amplitudes! Simultaneously at high amplitude
near the strike, and low amplitude far away from the strike. As the
"ocean wave" rolls on, the amplitude rises farther away.
Uh, "delta wave" is not a term known to me, but it's cute, and I'll
accept it!
This is simply not so - for current to flow at all there has to be a
difference of voltages. But if you are trying to say that
free-floating, unearthed (and well insulated from earth equipment is
safe because it experience zero voltage difference across it, I'd
agree! Let's all continue using airplanes.
Hey, let's not forget nanoseconds.

No, I can't take this very seriously.
Well, your point is what? That after a millisecond the first capacitor
across the rails blows apart? Personally, I wouldn't have given it more
than a few microseconds, but who's counting. Well, while it was taking
current it was keeping the voltage across it nicely down, in
conjunction with the huge voltage drop across the conductor (better
termed "resistor") leading to it. So it "protected" the rest of the
circuit for a bit, and then it popped, rather like the old waistcoat
button, straining the next one ...
Oh ho ho!
Except that you have forgotten that it has to get there first. And to
do that it has to get past a whole lot of other things that might well
be stronger, but which have to last out until then ... it's an
interesting exercise to compute the power time integral across
differnet bits of circuit and see which hits the limit first. My money
would be on the first parallel component in line, most of the time.

Peter

Lunacy.

13. ### Ron ReaughGuest

Possibly but NOT before ME, loonie.

14. ### Ron ReaughGuest

And may the force be with you, you sure need something.

15. ### Noel BachelorGuest

If you do a google search on his name, and you'll see he pops up like
clockwork whenever anyone mentions surge protectors, to spout his own
brand of 'myths'.

I thought he might quieten down a little after the hosing down he got on
rec.audio.pro late last year, but doesn't look like it.

Noel Bachelor noelbachelorAT(From:_domain)

16. ### Ron ReaughGuest

After faithfully doing this chinese firedrill for many years now and never
having even heard of anyone personally who has gotten anything fried, I'm
wondering if/when the day will come when I say to myself...enough of this BS
and just party on during the storm<g>.

17. ### Joe DavisGuest

After faithfully doing this chinese firedrill for many years now and never
I unplug my laptop from the AC and go on battery power. I'm connected to
the internet via my wireless router--if that takes a hit, all I lose is a
\$75 box.

18. ### Kent WillsGuest

I was just walking down the street, when someone handed me a piece of
paper. I thought it was something for a free meal at Popeye's
Chicken. Instead, I found that on 20 Sep 2004 19:37:36 -0700,
Odds are you would be safe, but it's certainly not dumb to
disconnect. It's far better to KNOW your computer is safe than to
take the risk and learn it's not.

Kent

19. ### Suraj SinghGuest

Surprised to see that no body talked about the capacitance of the
earth in this discussion.

Lightening do not bother to hit the airplane. Even if it does it do
not damage anything. Airplane capacitance is too small so a very
minute flow of charge can change its potential to match the cloud
potential. flow of minute change means little current ( micro amp)
which wont damage anything.

Imagine a situation where the plane has just taken off the ground,
lightening strikes its body and discharge to the earth through bottom
including pointed antennas in the wings; you can imagine the damage to
the circuit from where the antenna is connected.

As per the lightening is concerned one can not ignore earth if you are
close to it. You can dare to ignore if you are a much bigger mass
than earth.

You can raise the common mode potential of the system (say PC and
Modem), it helps but up to what extent? The charge on it will seek the
earth and if a short and quick high conducting path in not provided,
it may break down the air gap and discharge to the nearest path to
earth through the mouse wire.

Concept of GPR will provide much better protection if the whole house
is considered as a sub system. It will be economical too.
Power strips provide protection but for small surges only.

Best regards,
Suraj

20. ### Ron ReaughGuest

Nope, the full charge and current hits the airplane.
Just no.
If that happens then the antenna gets fried. Study up.
NO, through your toes first.
OH NO another whole world surge protection wacko.