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

[Suraj Singh]

Ron,
we all understand his simple point.
see between the lines.

"Ron Reaugh" <rondashreaugh@att.net> wrote in message
news:Kka4d.411297$OB3.318527@bgtnsc05-news.ops.worldnet.att.net...

"Roger Johansson" <no-email@home.se> wrote in message


It doesn't hurt the computer and other devices if the voltage is raised
a
thousand volts for a short moment, as long as all connections to it are
raised together. So the surge protector only has to keep all connections
at fairly the same voltage, even if they all are raised momentarily.
What
really hurts the equipment is if one of the connections moves far away
from the other connections, because then there is a surge inside that
piece of equipment, burning some component to pieces.

That is why the extension with outlets protected by a surge protector
works. It creates a subsystem which is kept together at virtually the
same potential for all connections to that subsystem.

What do you think up to what potential you can bring this sub system with
reference to the earth?
It may break the air dielectric from any point of the subsystem.

I too understand the theory and looks good theoratically. Unfortunately
real lightening hit do not follow these.
It do not follow ohms law either. air around just get ionised.

The first thing is to keep the same potential for all connection of the
subsystem.

this helps but this is not enough

Second point is, do not let the potential of subsystem (with respect to its
surrounding) rise/fall too much.

So providing a farady cage adds to the protection.


Suraj

When a modem is hurt by the lightning it is because the mains connection
to it and the phone connection to it are pulled apart by thousands of
volts, and that creates a damaging surge inside the modem.

If both the mains and phone line connections to the modem first have to
pass through a protector box, where they are prevented from moving apart
too much, voltage-wise, the modem is protected.


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

 

[Suraj Singh]

CLOSE ENCOUNTERS

Interesting...

http://www.kn4lf.com/kn4lf1.htm


nospam256k@yahoo.com (nospam256K) wrote in message news:<24a23015.0409201837.1b40dbcd@posting.google.com>...

Here in New York City (Manhattan) where I live, I usually use a laptop
computer running on an AC adapter, and get online via a dial-up modem
(phone line plugged into computer's built-in modem).

When it's merely raining outside, it's usually of no concern to me.
But when there's lightning or thunder, I quickly get offline, turn off
the computer, and literally unplug the AC adapter from the outlet, and
unplug the phone line from the computer.

This is done to avoid the possibility of the AC adapter or the modem
suffering damage from a voltage spike carried through either the AC
power line or the phone line (because of a lightning strike).

Does all this sound sensible to you, or am I being
overly/unneccesarily cautious?

 

[w_tom]

In order to confuse issues, some will hype nonsense about
airplanes and then post insults as proof of his superiority.
We are discussing a particular type of surge where a cloud
conducts to earth. That is completely different from
transients that transverse airplanes. Others have had this
explained to them previously. To subvert the discussion, they
insult and then throw in totally irrelevant topics such as
airplanes.

Once ionization takes place, then capacitance of both sky
(air) and earth becomes irrelevant. One of the best
capacitors is air. However air gets converted into a good
conductor (plasma) due to something called breakdown voltage.
We require protection and only discuss surges after ionization
has occurred. Surge current (not surge voltage) becomes the
dominant variable after breakdown voltage is exceeded.
Capacitance is made irrelevant.

Surge protection is about earthing an ideal current source.
A surge is a current source after ionization has occurred.
Voltage will rise only as necessary to maintain that current.
This is the point when damage can occur and when protectors
must shunt that current to earth. Concepts that apply both to
properly earthed 'whole house' protectors AND to properly
earth Franklin air terminals (lightning rods). They both do
the same thing. Divert the surge current to earth ground so
that the surge will not find destructive paths through
household electronics or church steeples.

Suraj Singh wrote:

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

 

[Ron Reaugh]

w_tom == Suraj Singh

Check the headers

 

[Suraj Singh]

Perhaps you do not understand the relationship between thunder bolt
and Earth.
Lightening always searches a better path to the earth through a
conductor and do not spare a non-conductor either if it needs.

Study up and try to understand this simple point.

Why the lightening is so hungry to get in to the earth?? Its the
capacitance of the earth.

The capacitance of the Earth is very, very large indeed. This means
that transferring charges to it will not significantly change its
potential, any more than pouring jugs of water into the sea will
significantly change sea level. So in the same way that we measure
heights and depths from sea level so we measure potential from that of
the Earth. We say that the Earth is at zero potential. The potential
of an object is the potential difference between it and the Earth.

The capacitance of a normal adult is about 160 pF. This means if we
walk along a nylon carpet and pick up a static charge of a millionth
of a coulomb we shall be at a potential of more than 6000 V! If we
then touch (about to touch) something earthed such as a metal door
handle we may feel a slight shock, but the charge transferred to Earth
is so tiny that it will do us no harm at all.

To protect CMOS chips from ESD we also connect a wrist starp to the
chesis and do not bother to connect the whole thing to earth. but
remember that lightening is not a tiny charge.

Read the last para of the following practical experience; see how the
increased protection was provided by a faraday cage.

http://web.ukonline.co.uk/freshwater/lightng.htm


Suraj


"Ron Reaugh" <rondashreaugh@att.net> wrote in message news:<rwJ4d.421086$OB3.324829@bgtnsc05-news.ops.worldnet.att.net>...

"Suraj Singh" <surajs21@yahoo.com> wrote in message
news:1998602c.0409231512.62c2a099@posting.google.com...
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

Nope, the full charge and current hits the airplane.

can change its potential to match the cloud
potential. flow of minute change means little current ( micro amp)

Just no.

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.

If that happens then the antenna gets fried. Study up.

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.

Huh?

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.

NO, through your toes first.

Concept of GPR will provide much better protection if the whole house
is considered as a sub system. It will be economical too.

OH NO another whole world surge protection wacko.

Power strips provide protection but for small surges only.

Nope.

"Ron Reaugh" <rondashreaugh@att.net> wrote in message
news:<ah64d.618488$Gx4.201449@bgtnsc04-news.ops.worldnet.att.net>...
"w_tom" <w_tom1@hotmail.com> wrote in message
news:4150E3FE.67C9A30C@hotmail.com...

A surge protector is only as effective as its earth
ground. A fact well proven even before WWII.

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

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.

 

[Suraj Singh]

Please stop writing abusive replies.

Checking the headers are your job. All others are here for helthy
technical discussion.


"Ron Reaugh" <rondashreaugh@att.net> wrote in message news:<uxL4d.421597$OB3.218482@bgtnsc05-news.ops.worldnet.att.net>...

w_tom == Suraj Singh

Check the headers

 

[Bob Ward]

On Fri, 24 Sep 2004 15:48:37 -0700, Kent Wills <compuelf@gmail.com>
wrote:

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 23 Sep 2004 16:12:57 -0700,
surajs21@yahoo.com (Suraj Singh) wrote:

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


Well, the OP did only ask about computers.

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.

Actually, airplanes do get hit. Probably more than most people
realize, although I don't have any actual cites to offer.

http://www.physlink.com/Education/AskExperts/ae568.cfm

Question

How is a plane protected from Lightning strikes?

Asked by: Sridhar Narayanan

Answer

Since the outer skin of most airplanes is primarily aluminum, which is
a very good conductor of electricity; the secret to safe lightning
hits is to allow the current to flow through the skin from the point
of impact to some other point without interruption or diversion to the
interior of the aircraft.
Estimates show that each commercial airliner averages one lighting hit
per year but the last crash that was attributed to lightning was in
1967 when the fuel tank exploded, causing the plane to crash.
Generally, the first contact with lightning is at an extremity...the
nose or a wingtip. As the plane continues to fly through the areas of
opposite charges, the lightning transits through the aircraft skin and
exits through another extremity point, frequently the tail (as shown
by Gauss's Law).

 

[Kent Wills]

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 Thu, 23 Sep 2004 02:16:01 GMT, "Ron
Reaugh" <rondashreaugh@att.net> wrote:

"Kent Wills" <compuelf@gmail.com> wrote in message
news:9ri4l0ho4nhr3fnogsjckf7h0palco26ul@4ax.com...
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,
nospam256k@yahoo.com (nospam256K) wrote:

Here in New York City (Manhattan) where I live, I usually use a laptop
computer running on an AC adapter, and get online via a dial-up modem
(phone line plugged into computer's built-in modem).

When it's merely raining outside, it's usually of no concern to me.
But when there's lightning or thunder, I quickly get offline, turn off
the computer, and literally unplug the AC adapter from the outlet, and
unplug the phone line from the computer.

This is done to avoid the possibility of the AC adapter or the modem
suffering damage from a voltage spike carried through either the AC
power line or the phone line (because of a lightning strike).

Does all this sound sensible to you, or am I being
overly/unneccesarily cautious?

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.

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>.

You'd most likely be safe having that party, but it's gonna suck
big time if your machine fries.

Kent
--
Nie'se schlect sim'wa

 

[Kent Wills]

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 23 Sep 2004 16:12:57 -0700,
surajs21@yahoo.com (Suraj Singh) wrote:

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

Well, the OP did only ask about computers.

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.

Actually, airplanes do get hit. Probably more than most people
realize, although I don't have any actual cites to offer.

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.

Kiss that antenna good bye. It's toast.

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.

Eh? If you had a much bigger mass than the earth, you couldn't
possibly be ON the earth. You couldn't possibly fit.

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.

Which is why I think everyone should invest in a wireless optical
mouse

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.

No they don't, actually. Power strips are nothing more than
additional outlets. Surge Protection strips can add a degree of
protection. These are two different things. Always keep that in
mind.

Kent
--
Nie'se schlect sim'wa