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

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.

Mmm. Very reasonable. Good explanation.

Peter

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

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 orig> w_tom wrote:

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 c> An apartment I was living in once took a direct hit. It's pure dumb

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.

Anyth> w_tom wrote:

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.

D> w_tom wrote:

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

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

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.

Possibly but NOT before ME, loonie.

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

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

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)

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.

BS

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.

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

What

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