Protecting Computers From Lightning? 83
rackrent writes: "I'm wondering what others do, both in their workplaces and homes to protect from lightning strikes. One look at Intellicast's lightning page should make us aware how often this must affect computers. Again, just curious as to what everyone does to safeguard their machines against lightning."
100% (Score:2)
there is only one 100% solution: redunand computing centers in a different solar system. You can get close though if you redunand center is on a different continent.
Re:Two things (Score:2)
Re:Protection? (Score:2)
As for trees growing deformed, that's nothing compared to the hacking that power company saws do to the trees to try and minimize the risk of branches taking out the lines.
I have buried lines in my neighborhood and I love them.
Re:What Ham Radio Operators do (Score:2)
Once the lightning ionizes the trail, all hell should light up...
Re:Two things (Score:2)
Re:Two things (Score:2)
Re:I saw this in a book (Score:2)
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Re:Lightning data currently unavailable. Hmm... (Score:2)
Bear in mind that any such thing that you build yourself won't be UL listed and if you start a fire with it your homeowners insurance might not pay out because of that.
Re:Please name the book (Score:2)
See alyandon's explanation [slashdot.org] immediately above for an excellent explanation of why overhand knots in the power cord work. I commend it to the attention of moderators as well. It is an excellent example of the type of comment that positive mod points are designed for.
See Mark Minasi's "The Complete PC Upgrade & Maintenance Guide" (9th edition = ISBN 0-7821-2357-0, published by Sybex) for one example of a book containing that technique.
Re:I'm afraid that doesn't meet minimum standards. (Score:2)
The faster the change in the level of current, the greater the opposition of the induced EMF in the original conductor. This opposition, called inductive reactance, increases as frequency increases.
Any time a wire is looped back on itself, whether as a turn in a transformer coil, or a knot in a power cord (remember, the "hot" and "neutral" lines are connected to each other through the load and through the source, and the same current that flows down one flows back up the other, they're part of the same series circuit), or as a twist in unshielded twisted pair (again, both conductors are part of the same circuit), the inductance is greatly increased over what it would be without any "looping", because the proximity of different parts of the same conductor to each other intensifies and reinforces the magnetic field.
The power surge that tends to burn out equipment isn't the original lighting bolt, it's EMF induced in the electrical lines by the lightning. This induced "spike" tends to have an almost instantaneous rise-time. Therefore it can be considered a very high frequency current. An inductance (coil, loop, twist, knot, etc.) with negligible reactance at 60 Hz is going to have a very high reactance, or opposition, to that spike's much higher frequency. Most of the spike's energy is going to be used up in trying to shove current through that high reactance knot. The voltage drop across it, the difference in potential, is going to be most of the total voltage of the spike. Most of the total energy in the spike is applied to the knot. This high voltage will probably cause enough current flow in the knot to burn up the insulation and possibly partially melt the wire itself. If that spike didn't drop off as fast as it rose then eventually it would force a destructive current through every path it could find, knot or no knot, but fortunately individual lightning strikes end as quickly as they start.
Re:What Ham Radio Operators do (Score:2)
Re:Here's an interesting idea... (Score:2)
I run a paranoid power system. Everything goes through the sacrificial surge protector. After that is the TripLite line conditioner. Then there is a UPS for each computer. Computers are either directly pluged into the UPS or have a surge supressor between them and the UPS. The phone line for the DSL has it's own surge supressor too. After my appartment building was hit I didn't have to replace any of my electronics, but I did replace the sacrificial surge supressor and line conditioner. Other people in the building were replacing everthing.
Re:Protection? (Score:2)
Here's an interesting idea... (Score:3)
Cheers,
levine
One More Thing... (Score:1)
Re:Depends on what you mean by lightning... (Score:1)
UPS (Score:1)
Lighting arrestor and home surge suppressor (Score:3)
Also put in a surge suppressor on your circuit breaker panel. A whole-house suppressor is slower than the type used on a power strip, but can handle much more power. This will divert large surges, and is actually to protect the smaller surge protectors.
Finally, use the power-strip style surge protectors. These are delicate fast-acting suppresors which can protect your devices from minor surges.
Here [phoenixcon.com] is a description of this multilevel protection.
Re:What Ham Radio Operators do (Score:1)
Won't happen (Score:1)
That won't happen..
Not because the company won't pay, but because the damn things WORK.
I worked in computer sales for a few years, and I had one customer that lived out on a farm, and his house was hit by lightning at least once per year.. when he bought his computer from me, I sold him a TripLite surge supressor (it had one of those $25,000 guarantees)..
When spring rolled around, he brought the surge supressor in to us - he said that his house had been hit the previous night.. among other things, the lightning toasted his microwave, and every light bulb in his house had exploded..
The supressor smelled like smoke, rattled when you shook it, and had what looked like "blast marks" coming out of it.. he said that his computer was on when the strike hit, and when the storm was over, the computer still worked..
We exchanged the supressor for a new one (it had a lifetime warranty, which was covered by the lightning strike) and he went on his way.. he said that this was the best $100 he'd ever spent..
Guarantee (Score:2)
Insurance is vital (Score:1)
Re:Protection? (Score:2)
The only equipment to get fried was stuff connected directly to telephone lines (modem, answering machine, phone, fax).
For the average user, a $15 power strip/surge protector is probably enough. For the paranoid, get something with a replacement warranty. It may not work any better, but at least you'll get a new computer if you do get hit by lightning (and the magic smoke is released).
Re:Related Question (Score:1)
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Re:One More Thing... (Score:1)
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Re:Depends on what you mean by stopped... (Score:2)
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Re:Protection? (Score:2)
For the paranoid. [polyphaser.com] We have one of their systems in our house. It'll take most anything that comes through the power line and re-nice it. Hell, I doubt I even need to use surge protectors anymore, but like I said, only paranoid people like me buy this stuff.
Re:Protection? (Score:1)
The point, I suppose, is that even without wires in the ground (and we do have below-ground power lines) lightning can do nasty things with burried utilities.
Re:Related Question (Score:2)
what i do at home.... (Score:1)
I go to school in milwaukee, Wisconsin though, where they have plenty of thunder, but the dorms apparently have power under control... there was one outage the whole time i was there, and it was unrelated to nature as far as i could tell... all the nature had no effect on my computer
Re:Two things (Score:1)
icanneverbereached@sogoaway.com aint my address.
Bob Villa and Goodbobjob on track (Score:3)
You will be a happy camper if you then have a surge protector too. This should stop all but a direct hit on your house. The power coming in is like a magnet I'm told. If you are going to get hit it will almost certainly be on or around where the power comes into the house. (I am not an electrician...)
Okay, we got the power covered, goodjobbob told you not to forget the modem, easy to do, but many of the surge suppressors have a built in line protector. However, remember that Cable/DSL modem too. You probably accepted responsibility for it when you got it from your broadband supplier. Have a UPS? Front end it with a protector. Even though it has one built in, the UPS is much more expensive than the protector is, so save it from itself.
My approach is that if it in any way, shape or form enters equipment from outside the house I put a protector on it. That would include your stereo, TVs, DVD player, VCRs, regular phone (the 2+ghz one that set you back $100) all that fun. I try to buy names I recognize and that can be screwed into places. This lets me hide a protector on the back of the stereo cabinet, etc.
Next check out the insurance policy. Why after putting all this in do you need to worry? Sorry but a direct hit is coming in, jumping through most everything and ruining your day. That is also why, in severe thunderstorms, if possible I unplug the computers and the phone lines.
Life's not fair, but it beats the alternative...
Re:Here's an interesting idea... (Score:2)
I had a near strike with lightning, the surge protectors all worked, I just had to reset my alarm clock, microwave, etc. But I had this weird phone problem for days...
It seemed like sometime during the night, my phone line would go off-hook, and nothing would reset it until I went around and unplugged all the phones. Finally, I tracked it back to the plug my modem was running off of. Except my modem worked fine...
A little more experimentation, and it turned out that something in my modem got fried by the lightning, and it could no longer hang up completely. The connection got dropped, but the next time you picked up the phone, you got a dead line. Unplug the modem from the wall and all is well again, until you dial the modem.
The lessons I learned? Always have a surge protector on any phone line running into an expensive device. And keep all your warrenty information handy - I got the manufacturer to install a new modem for free.
Re:Bob Villa and Goodbobjob on track (Score:1)
Re:I'm afraid that doesn't meet minimum standards. (Score:1)
Malcolm solves his problems with a chainsaw,
Re:I'm afraid that doesn't meet minimum standards. (Score:1)
Malcolm solves his problems with a chainsaw,
Even the best UPS . . . (Score:1)
Re:for the record... (Score:1)
In truth, this is my normal practice
Having once lost a mobo to a surge, it helps my peace of mind.
Regards,
ninewands
Re:What Ham Radio Operators do (Score:1)
Un-screwing the connectors to a 10-meter antenna, by hand, during an active and immediate electrical storm doesn't sound like good risk management.
UPS (Score:1)
100% is very hard. (Score:1)
Protecting against a direct hit is harder. Think about it - this bolt of electricity is zapping across a 2-5 kilometre air gap with not much problem. You can't stop it, you can only try to divert some of the energy away. So your surge suppressor MUST be WELL GROUNDED. With a bad ground everything could go through your equipment.
One of our customers sent in a modem for repair one day and I noticed that some of the copper tracks had _evaporated_ and the copper was deposited in small little spheres on the inside of the container!
I called them up and asked them if anybody was injured (and to tell them the modem was beyond repair). They said nobody was around at that time, but almost everything got zapped. The computer's mouse was also fried!
We supplied them different sorts of lightning protectors - a more expensive 3 stage one for the plantations, and a single stage one for cities and towns. Unfortunately they had put the single stage one at the plantation (despite us telling them where to put their stuff).
My own home built protectors consist of MOVs and GDTs (Metal Oxide Varistors and gas discharge tubes). You could also put in fast blow fuses for the phone line (not for the power line because most CRT monitors draw in a lot of current when you switch them on).
My powerline has an MOV across the live and ground, and it then leads to a Blackout buster UPS, and then only to my computer.
The phone line used to go through the GDT and then to the UPS phoneline protector and then to the modem.
Got hit badly once, at the power plug the 13 amp fuse got burnt and the MOV blew up, and the UPS was KO'ed. Not only that, the phoneline copper connectors were welded to the UPS phoneline jack!
The mains circuit breakers were fried too.
But amazingly the computer and modem were fine
Got a replacement blackout buster under warranty two weeks later. Fortunately no strikes during that time!
Link.
Re:Two things (Score:1)
Actually it is...I had a setup running cable (TV) into my VCR and then RCA to the video in on a box. (Use my monitor for a TV these days).
Anyway. I had powered down the works in a storm. Lighting hit nearby (not even a direct hit). VCR recovered. Video-In card did not. $300 bucks vs $75 strip.
The school I used to go to lost 20+ modems from the phone lines being hit.
Gotta love those mid-west thunderstorms
Re:I saw this in a book (Score:1)
Re:Two things (Score:1)
1. Backups to tape/cd. Offsite backups to tape/cd. If your house gets a direct hit, and burns, and your tape/cd burns with it, you're going to be upset. Get the cheapest safety deposit box you can at a bank, a DAT tape, travan tape(ick) or cd fits easily.
Myself, I'd backup to a hard drive in a removeable hard drive carrier, AND cds. Toss that hard drive in an anti-static bag and seal it up, and put that in the bank box CD's are in case someone besides your box, has a collection of rare earth magnets that they didn't want stolen.
Keep in mind, in the event of a police investigation/etc, your bank deposit box is likely to be opened. Encrypt.
A good battery backup is a good defence, make sure you get all your paths covered.
Depends on what you mean by lightning... (Score:3)
This is what I tell most of our customers when they ask about lightning: "If your antenna is directly hit you're pretty much screwed". (Acutally this might be a good place for an appropriate goatse.cx link to illustrate how badly screwed).
I then go on to say that 99.9% of the damage is actually not caused by a direct hit. In fact, the purpose of most "lightning arrestors" is really to drain/discharge the static an antenna picks up.
This also applies to Power/Phone/Satellite TV, etc. etc. etc.. If lightning hits the pole outside your house, you probably will loose equipment. My personal experience is that even if the stuff doesn't immediately fail, you will have ongoing problems with anything exposed to that level of problem. Yes I've seen it.
That said, you can protect yourself in most less extreme cases. Unplugging EVERYTHING is always the best option but in reality isn't really an option for most people. The path I take is to go buy the best surge suppressor and/or ups that you can find. I personally prefer APC's. Most, if not All APC units include an equipment replacement guarantee so if you do take a direct hit you're covered. Remember to supress EVERYTHING. The power line, the phone cord, the satellite antenna cable plugged into the satellite receiver attached to the same power strip, etc. etc. etc. Lan surge supressors are highly recommended, especially if you go anywhere near outside with the cables, or to a "non protected" hub or similar.
Generally for the protection warranty to be effective you must make sure everything is protected or the warranty is void.
Hmmm.. I'm sure there's something else I wanted to add, but I'm not sure what, so I guess I'll quit rambling :)
And remember, off-site backup is always a great idea...
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Household Suppression, no loose ends (Score:2)
Let's assume that's not good enough, and you're developing hardware you can't buy again. The obvious answer is to unplug it when there's a storm - including any networking or modem lines. But let's assume you have to stay online if possible.
Get a heavy duty surge suppressor - I got one from intermatic http://www.intermatic.com/comind.htm#3 for around 100USD (installed, actually, but at the same time I was having my service upgraded) I had a long talk with a senior developer there - they aren't warrantied against lightning; they're not in the warranty business. But they've saved equipment from lightning in the past.
Then get something for all your critical systems: Small cheap surge supressors are really designed to save your computer from the surges caused by your AC (or any other dirty device) and nothing as powerful as lightning. OTOH, if you're lucky it'll melt into a puddle when the lightning hits - and do it fast enough to save everything downstream. But they're better than not having them. Good ones are better. UPS Power Conditioners are better. (see also insurance, above)
I like the coil idea, although I can't guarantee it'd work, I think it'd be worth it.
Make sure your grounding is good - strong connections.
In general, btw, I prefer to keep electronics on separate circuits from anything else (esp motors, like AC, refridgerators) I don't think this would help in a lightning storm, but it cuts down on line noise.
I guess that's it. Good luck.
Re:I saw this in a book (and use a GFCI). (Score:1)
That's why you get RF leak from coax if there are kinks or knots in a line and why network cable (especially cat 5, 5e, and higher) should have no kinks, knots, or sharp bends in the twisted pair.
It makes very little difference for low frequencies, such as 50/60 Hz AC and lets it pass. In addition, the knot becomes an inductor. Inductors have progressively higher and higher resistance to higher and higher frequencies.
So, it sounds good on paper. I'll try it, myself. During bad storm years, like this one, we in Kansas get a lot of lightning. During really bad storms, we also get hail and tornadoes, which produce even more lightning, rain, and other storm artifacts, most of which make it even harder to protect your equipment.
Oh, and be sure to plug in to a GFCI, a Ground Fault Circuit Interruptor!!! A poorly grounded circuit, or one not protected from ground faults are even *easier* prey for lightning. In a strike, they could disconnect you from the circuit, perhaps, maybe, because the electrical ground may be screwy, with lightning and your surge suppressor duking it out. It takes about 1/40 second for most GFCI's to work, so don't expect miracles, but it's a few bucks well spent.
You can pick one up for about $6.50 USD at Home Depot, Lowes, or your favorite hardware store. GFCI's are the outlets with the RESET and TEST buttons, used in kitchens, bathrooms, out doors, and other places where there might be water, dampness, or ground faults.
A GFCI can also protect you from electrical shock.
So, do all the above: a GFCI, an overhand knot, and a good surge suppressor *with noise filter*.
Re:Two things (Score:2)
I would say that having using the coax protection is probaly not worth the extra money for the surge strip. (The ones i've seen are like $50-75)
Two things (Score:3)
2. Insurance - rental insurance is cheap and homeowners insurance is a necessity. Most insurance companies will cover such damage.
If your house gets stuck by lightning, and your house doesn't have a lightning rod or grounded antenna, most of the electronics in your home will be utterly destroyed. If your house or power pole gets hit by lightning, the current will arc across the blown fuse of a surge protector anyway.
You Can't Hide (Score:1)
About half the desktop computers and printers started to smoke. After the panic was over, I found machines that had charred serial ports, and/or charred parallel ports, and/or smoked Ethernet cards. Some of the motherboards were burned up, too. Laser printers took an awful beating, lost several (which made for good dumpster diving later
What I learned is that:
Re:grounding (Score:2)
I know all slashdot readers are electrical engineers in their spare time, but:
If you install additional grounds (for computers or whatever) the must all be bonded together. Bonding involves runing a piece of heavy copper (10+ guage) between all grounds. Different parts of the grounding system (Water pipe, copper ground rod, building steel etc.) have different potentials (sometime several volts or more). Without a proper bond, grounds in network cables can (and will) carry the load.
My wife worked for a local government that had a network bridged between to sections of a building. A construction error cut the bonding wire. The current flowing between the grounds on the network cables caught several computers on fire. Their unique system of troubleshooting (plugging in computers and waiting for them to smolder) is another story.
Anyway, bond those grounds. If someone tells you that you should have an Isolated Ground (a very bad idea) know that they are spouting BS. It only takes one link to equalize the potentials, your choice a 24 gauge network cable (and your computers innards) or a nice piece of 10 guage copper(or larger)
Re:You Can't Hide (Score:2)
What Ham Radio Operators do (Score:5)
Many Hams use products from PolyPhaser http://www.polyphaser.com/ [polyphaser.com] that are designed to handle a direct strike. They also have information on "What is Lightning?" [polyphaser.com]
Also, the ARRL [arrl.org] has the ARRL Handbook [arrl.org], which has information on Lightning and protection as well.
Lastly, Don't forget that the Telephone line is a very common way for the lightning to enter your equipment.
What do I do in known lightning storms, besides the PolyPhaser protection? I disconnect my antennas and place the ends in a ceramic jar (Just in case).
Re:One More Thing... (Score:1)
Think about it: You go to great lengths to encrypt your email, rotate your passwords, block malicious Internet traffic, etc etc etc -- then you do a full system backup and leave it in your car along with your stereo system just begging to get stolen.
I am not saying that most stereo theives would know what to do with it... but do you want to take that risk? Here I think the cure is worse than the disease...
Re:88mph (Score:1)
Lightning data currently unavailable. Hmm... (Score:2)
But seriously, As an added precaution (and in keeping with the DIY spirit of most Ask Slashdot questions), I saw a really clever surge suppressor design. I can't find the original to credit it, but it's very simple: Just some bidirectional large zeners (with appropriate holdoff voltage) in a replacement 3 prong plug, inside the cap with no cord attached. Portable surge suppression, and IIRC, zeners are right around the correct frequency response for lightning, and usually large enough to sustain a smaller hit. $3 of components makes your $2 surge suppressor a $25 surge suppressor!
Re:Lightning data currently unavailable. Hmm... (Score:2)
Yes, most transient protection zeners just call them 'bidirectional.' You get the same zenering voltage in either polarity.
Bear in mind that any such thing that you build yourself won't be UL listed and if you start a fire with it your homeowners insurance might not pay out because of that.
Good warning. IANAL, and all that.
I saw this in a book (Score:1)
and in the book it mentioned using Overhand knots in the line to protect against Lightening.
Basically, the power of the charge will burn out the cord when it crosses over itself like that.
The guy in the book said he had a giant thunderstorm one year, and all his stuff with Overhand knots survived, while most everything else didn't.
The Author was Mark Minassi or something like that.
grounding (Score:1)
Re:grounding (Score:2)
IANAEE, but I can vouch for the importance of this. A company I contracted with had underpaid and incompetent monkeys wire their building, and the monkeys forgot this step. A few months down the road, EVERY single UPS connected to that circuit was fried in an instant. Luckily for them, they had every single PC plugged into a UPS, so no PC's were damaged. The 40 or so UPS's weren't so lucky, however. (You can take that as a vote of confidence for APC UPS's as well....)
Re:You Can't Hide (Score:1)
It sounds like the serial/parallel/lan was(were) not properly grounded.
mf
Bob Villa always says.... (Score:1)
Be sure to protect your modem too, a surge off a telephone line can be every bit the party one from an outlet is. Myself, I just use the $10 dollar jobs that protect your modem too.
Lightning protection... (Score:1)
On my Linux machines I use nothing because we all know God smiles upon Linux users, just as the mods do on Slashdot. I have nothing to fear when I use Linux.
Just kidding about the taters.
Re:Guarantee (Score:1)
By the way, I believe I may have found your lost packet. I do not have an OC3, but I have a packet similar to the one you described. If you can have an OC3 run to my house for a month, I'll try to coax it onto the line and return it to you. However; it may be more affordable for me to print its contents out and mail them to you?
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Re:Household Suppression, no loose ends (Score:1)
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Related Question (Score:2)
I've got a cable modem. If some anarchist down the street 'accidentally' manages to jam his cable connection into a 240 VAC socket at his house, what's going to happen? Do ISPs have gear to protect against anarchists and such? Or would every computer on the street suddenly go up in flames? I'd like to think that people thought of this way before me, but I can't help but wonder. (Perhaps this is reason enough to get an optical Internet connection? ;) )
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Re:What Ham Radio Operators do (Score:1)
As for snapping, solved that making everything close as possible and some tape, I realy don't know about the burn problem, strikes often happen within a blink of the launch.
Don't laugh, the people down in edgewater don't like me one bit. but the cops can't do anything because all that is left is parts of the launch platform. besides I think they would get a kick out of it.
I have a question. I am scared of filming this because the lightning sometimes get real close ( about 50 feet from my car but there are 2 parking poles in the way ) anybody know how I could prevent killing my cam corder ?
side note: only launch when the wind goes away from you and homes, the small rockets I use normal fly 10 to 20 degrees off due to the wind.
also tungsten wire from the weilding company is too thick. but might work if your willing to make the lauch platform higher.
ONEPOINT
Re:What Ham Radio Operators do (Score:1)
Never thought of that. I sure would like to know how much thrust I would need just to get a good straight launch.
onepoint
Re:What Ham Radio Operators do (Score:2)
But I would like to add one more piece. I have a sump pump in the basement. the water pours into it from a steel pipe. I have added an extra wire from my shielding to the pipe. I don't know if it helps but I feel just a bit safer having an extra ground.
offtopic : Want lighting to strike real near durring a storm.
all you need is copper wire ultra fine diameter ( 1200 feet as thin as hair ), a very good rocket with motor( needs to be able to go 2000 feet), and a very large public park.
Coil the wire on a cone otherwise it will snap.
Secure copper wire to rocket, Ignite it without touching it ( monofiliment triger switch about 150 yards away ) attached to your car will work. go in reverse and see the show.
It's real dangerous but there is nothing better than having lightning strike right next to you.
ONEPOINT
unplug it (Score:1)
Re:What Ham Radio Operators do (Score:1)
Protection? (Score:1)
There is *no* way to protect your computer from
a direct hit; all the surge protectors you put
in place just become another target of the millions of amps coming from the sky
88mph (Score:1)
It turns out that this set-up also provides superior protection against Libyan nuclear terrorists and crewcut browbeating types.
Please name the book (Score:1)
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Depends on what you mean by stopped... (Score:1)
You're absolutely right about surges on wires. (For the uninitiated, when lightning strikes the ground the current of the bolt is enough to raise "ground" potential by hundreds or thousands of volts (by Ohm's law, V=IR). This voltage can travel easily over low-resistance paths like power wires; if this region of elevated ground potential includes the ground rod for e.g. your electrical substation or your power meter, there can suddenly be hundreds or thousands of volts of difference between the power leads and the ground at your house.) If you don't have surge suppression to dump these transferred currents back to ground, equipment can get voltages far beyond what it's designed to handle.
Aside: Isn't it odd that there is no obvious attempt to market optical-cable connections for e.g. modems, to eliminate the surge issue?
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I'm afraid that doesn't meet minimum standards. (Score:2)
Why don't you go back and study some more until you're able to explain exactly what an overhand knot does that is helpful, and how it works.
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Re:I'm afraid that doesn't meet minimum standards. (Score:2)
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Oh, puh-leese! (Score:2)
But it's worse than that! The line cord consists of at least two and usually three conductors in parallel. Winding the cord into a circle only protects against common-mode transients; if you have a large surge which places the power-supply hot conductor at 900 volts WRT the neutral and ground (which are connected together at your main panel), your overhand knot will not protect you at all. The current surge will go through the coil one way through the hot conductor, fry your gear, then exit back through the other conductor(s); the net current through the coil is zero, so the protection against differential-mode surges is also zero.
And you know this how? (Exactly how do you get an "almost instantaneous rise time" in a current going through a path several miles long? There's this little thing known as speed of light delay, plus inductance in the plasma which carries the bolt itself...)Just from simple V=IR calculations it's easy to show that a 50,000 amp lightning bolt striking near a transformer where the ground has a 0.01 resistance will displace the ground voltage from "earth" by 500 volts. This will displace both neutral and hot at the transformer if it is grounded. Neutral will be re-referenced to ground at your service panel, but hot won't be; this allows the voltage surge to come in over the hot lead. Voila, hundreds or thousands of volts at your power supply. This is what lightning arresters and surge suppressors are for: to clamp the voltage, dumping the current to ground and dissipating the excess in IR losses in the conductor upstream (the conductor is a lot heavier and able to take punishment than your equipment probably is). Ferroresonant transformers (Solas and such) do a pretty nice job of regulating voltage excursions and eating spikes, but they do this with large hunks of iron and variable-saturation tricks. One-turn knots in line cords? Don't make me laugh. It didn't take me very long looking on the web before I found specific recommendations against knotting electrical cords [belgrade.com].
Now go away or I shall have to taunt you again.
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for the record... (Score:3)
I came home once to find that my sister had plugged her surge protector into yet another surge protector, I loved it. Just an idea. I don't think it will do anything, I just got a kick out of it.
Re:Protection? (Score:1)
The strange thing is, I've had a number of bad lightning strikes a few hundred feet away from my house, because I live on a hill. There have been no power surges from the power lines. The only surge I've had was during a sunny day in the early morning, and it blew out everything except my computer and the TV, which were unplugged.
Re:You Can't Hide (Score:1)
Check your power quality while you're at it.. (Score:2)
(Sorry, only applies to US, if anyone else wants to add on for European and other international standards feel free) 1) check your hot to neutral voltage: set your multimeter to Voltage AC and make sure the probes are plugged in for voltage, not current, measurement, consult your meter's manual. Put the red probe in the smaller outlet slit (the hot) and the black in the larger slit (the neutral) (although it really doesn't matter which one, its AC) You should read some where around 120volts +/- up to 2%, any more or less and you might want to check with your electrician.
2)check ground connection: Although this doesn't help with checking the current capacity of your ground, it at least is a decent check to see if its connected. Keep the red probe where it is (in the hot) and move the black probe to the ground hole (semicircular shaped), You should get about the same reading you got for step one, usual a little higher especially if there is a lot of current on the neutral. If you don't, make sure you have the red probe in the hot, try the red probe in the larger slit just to make sure. (your hot and neutral may be reversed, although this is pretty rare)
3)check your neutral to ground voltage: which if you do the math from steps one and two you can figure out. Put the red probe in the larger slit and leave the black in the ground. This reading is usually in the tenths of volts if anything. If it is much higher, and your step one reading is not in range, then you may have an over-loaded, or poorly supplied circuit. (i.e. you have to much current current on the netural, or a highly resistive neutral, or a low volate on the hot)
I hope that helps, an even easier way to check that just your hot, neutral, and ground are connected properly is to get one of those outlet testers at your local hardware store. And as long as you don't touch the probes together, or to yourself, when they are in the outlet, you should be safe, but if you are unsure read the multi-meter manual or use the outlet tester...Here's [copper.org] a decent intro to power quality issues, they mention stuff about switching power supplies, like those found in computers and other interesting topics on power quality...
The cheap solution... (Score:1)
We had someone come in with a pair of wire clippers, and clip all telephone, power, and network cables. This proved to be a life saver, since the other day a storm came through and took out the systems of several surrounding businesses. Our systems were untouched, however.
We HAVE had a problem getting dial tone, or even getting our desktop machines to boot, but we've resorted to bird watching on the back balcony now. Management wasn't too thrilled, but us techs knew we had to cut equipment loss costs in today's dot-bust industry... so......