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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."
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Protecting Computers From Lightning?

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  • by bluGill ( 862 )

    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.

  • Be sure to check the size of your box. CDs do _not_ fit easily in our box, because of a lip on the top of the box. If that is a problem, you may want to hunt down the smaller size CD-Rs (80mm?) and use those for backups. Not as capacious (and more expensive), but presumably your porn video collection isn't your most important data.
  • Also with underground lines, even though there are backhoes and tree roots that will take them out on occasion, you don't get huge areas with lost power during bad weather (unless the substations go). So they should be able to get a crew out quickly and get your service back.

    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.
  • I was thinking how to get a rocket to spool a lenght of wire at the end without breaking or melting away. Try a length of tungsten wire or rod (about 3 or 4 feet) near the rocket's engine if the copper wire melts due to the heat from propulsion. The rest of the copper wire can pour off the bobbin with the end taken off toward the ground.

    Once the lightning ionizes the trail, all hell should light up...
  • Be sure to check the size of your box. CDs do _not_ fit easily in our box, because of a lip on the top of the box.
  • Those small disks max out around 150MB. That's too small....
  • Hrm, sounds like a cheap, fast and easy way to protect stuff and sounds plausible. Anyone else heard of this?
  • When you say bi-directional Zeners I assume you mean connected cathode to cathode or anode to anode?

    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.

  • Go back and study some more. Study until any mention of wires in the same circuit crossing or twisting around each other automatically makes you think "inductance".

    See alyandon's explanation [] 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.

  • All wires have inductance. If current flows through them there is an associated magnetic field. Any change in the level of current causes a change in the magnetic field. Any change in that magnetic field induces a current in any nearby conductor (or at least a voltage difference between the ends of that conductor that will cause a current if it can find a complete path), including the original conductor through which passes the current which generated the magnetic field in the first place. In that original conductor the induced voltage, or electro-motive force (EMF) is in reverse polarity to the original voltage, or EMF. Any change in the original EMF level causes an EMF that fights the change in the original. It's kind of like a 3 battery flashlight with one battery turned the wrong way, you subtract its voltage from the total voltage of the other 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.

  • Wire guided anti-tank missiles use a similar system. There is bobbin of wire on the back end of the missile. The ends of the wires are connected to the guidance electronics. The wire peels off the back of the bobbin as the missile goes down range.
  • Unfortunately you can't always unplug the computers as you are away from home or running servers [] on them.

    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.

  • For the record, underground utilities actually have more problems with lightning. When lightning strikes a spot, it goes through the ground for some distance. As such it usually finds the underground wiring.
  • by Levine ( 22596 ) <levine.goatse@cx> on Tuesday June 26, 2001 @05:52PM (#128300) Homepage
    When storm clouds are brewing overhead and lightning is striking all around you, how's about turning off and unplugging your computer from every place it connects to the wall? No process is worth so much that its clock cycles are more important than the thousands of dollars you've invested in your computer[s].

  • ...because you'll find going to the bank is inconvenient, have a little box in your car to put your backups in. As soon as you make a new backup, take it out to the car. There's a better chance of the backup surviving when it's in the car than in the house -- unless your car catches fire in the garage and that's what burns down your house.
  • Yes, if a lightning bolt hits your house you have to assume all your electronics are destroyed. Any spark with enough power to jump across several miles of air isn't going to be stopped by any insulators or suppresors. The cables to ground which are used in lightning rods and arrestors simply try to provide an easier route for the main bolt to follow. Despite that, the ground around your house will briefly have an electrical charge of hundreds or thousands of volts, and all your electrical equipment is connected to ground through the third wire as well as through one of the two "power" leads. There are plenty of opportunities for undesirable current flow in this situation. Go ahead and install lightning protection, but also protect against the more likely surges from nearby strikes.
  • by SEWilco ( 27983 )
    Of course, a UPS or constant-voltage transformers can also be put on devices to give a different style of protection. (As I mentioned everything else, I should have mentioned this too...)
  • by SEWilco ( 27983 ) on Tuesday June 26, 2001 @04:13AM (#128304) Journal
    Yes, you can put a "lightning arrestor" on your cables -- this tries to divert a direct strike or near miss, mainly to prevent fires.

    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 [] is a description of this multilevel protection.

  • I run several repeaters and have a good deal of protection on them, but I don't expect it to take a direct hit. In the event of a direct hit I expect to change frequency to something that hasn't taken a direct hit and replace/repair the equipment later. In the event of a hit you should be more concerned with the house not burning to the ground than the computer. What you want to protect against is the electrical currents flying around in the atmosphere that don't show up as lightning. I have watched hardline coax sit on the floor and arc when the cloud to ground action was several miles away.
  • I'd like to see someone claim that money :-)

    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..
  • APC [] has something like a $25,000 guarantee for power surges. I personally have seen an APC surge protector melted to a puddle of goo, and the equipment plugged into it was just fine after a new power cord. (The end melted into the surge protector.) I am absolutely sure that the $50 more you spend on a good surge protector is worth every penny. APC also makes UPS units with the same capability (as far as surge protection), as well as other line protectors such as CAT5, phone, and COAX. Protect every line going into your datacenter and if anthing gets hit by lightning, APC will write you a check to repair the equipment. See their site for the details.

  • I have everything that is being discussed here. I have the lightning supressor on my home, APC ups and surge supression, all phone lines are supressed,... etc. In the last seven years I've had to make two claims against my home insurance to get replacements. In one case I found out that all of this stuff doesn't protect the ground wire. There was a large power cable disruption right outside my house during a heavy thunderstorm. I lost power and at the same time there was plenty of power right next to the ground wires. :-) Confused the poor electic company trying to understand how so much stuff got smoked, until they checked where the break was in comparison to the lightning supressor and the grounding pipe. :-) No matter what you do, you cannot 100% protect the electronics. Something can still go wrong and the rider that I've added to my home insurance has paid for itself easily. It even covered a surge wasting my Air Conditioner Compressor. Most plans allow adding a rider for this kind of protection and usually it isn't too bad. Some plans now include it as part of normal coverage because of the increase in electronics in home. I originally got my insurance because it also covered fire. I thought that would be the only way that I would ever have a claim. I was very wrong on that one.
  • My family's computers survived a direct strike with nothing more than your average $15 surge protectors. What do I mean by direct? The lightning hit the power pole 20 feet from my house and blew up the transformer.

    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).
  • With an optical connection, you'll only fry your own line, but you won't affect others. Fiber runs point-to-point, the cable media is shared.
  • EXCEPT when you live in a place where the climate isn't relatively stable. We poor SOBs in North Dakota have an average yearly temperature range approaching 150F. Frankly I'm not going to put my backups in my car when it's either -50F or 100F outside. Temperatures like that are more than enough to destroy most backup media.

  • 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? What would this be? Just a very short length of fiber with a cheap led at each end to convert from the electrical signal to the fiber? I'd buy one. Go forth and find ye' a bakcer.

  • No.

    For the paranoid. [] 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.

  • When lightning hit the tree in my front yard it traveled through the root to the underground gas lines, traveled along that to both my house and the neighbor's, and then ruptured the line when it reached the meter in both cases, only at my house there was a fire, at the neighbors just a leak (not a good combination). Luckily the winds dispersed the gas and the heavy rain prevented the house from catching on fire.
    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.
  • Well, thinking as an 'anarchist' might, I would simply swap a 240 VAC line for a high-powered laser if they switched to an optical connection. Voltage spikes are to be expected, but who's going to protect from an optical burst? :-)
  • i live in coastal southern california, the last lightning storm (at home) that i can remember was probably 2 years ago, and far enough away that i could barely see the flashing. Although, with my new CB radio I could hear it great, it was nifty :)

    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 :)

  • 3) Get a power strip that will do phone line protetction. (I'm in an area where DSL is just out of reach, cable modem is non-existant for 1-2 years, and sattelite-internet still costs $80/month and $800 for hardware, so I'm still stuck at dial-up). I just had two people come into my office (IT Dept) asking me to look at their home machines, and one had a modem that fried, the other had a motherboard that fried (I didn't get a chance to test that modem). Both insisted they had their computer plugged into a power strip, and there were no electrical surges at their house, but both were dialed up during a lightning storm. Slightly offtopic: I've recently been seeing some power strips that claim to protect "cable TV" lines. Granted, you should have your sattelite dish properly grounded when installed, but does anyone know if these strips are worthwhile sticking in-line to your dish and receiver? aint my address.
  • by Kefaa ( 76147 ) on Monday June 25, 2001 @08:40PM (#128318)
    For the home/small business network, Home depot does sell a unit as described above and it took about 15 minutes to install. It will absorb the hit, however your house will pass some of it along the circuits. I believe they are really designed to stop a fire more than anything else.

    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...
  • The difficult part comes when the storm strikes while you're out of town, or even at work.

    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.
  • I don't know about ALL of them, but I know most APS and my Kensington surge protector comes with a 10,000 dollar surge-damage gaurentee. Basically, they'll pay for anything behind their unit that gets toasted. I'm sure it takes forever, but it's nice to know that it's there should the need arise.
  • I belive what you are seeing is not the electricity, but ionized air, which would stay around for a bit after the electricity that caused it went away. Also, part of what you are seeing is probably an after-image.

    Malcolm solves his problems with a chainsaw,
  • Yes, because it is the ionization of the air that interferes with the radio.

    Malcolm solves his problems with a chainsaw,
  • There's no substitute for a really good UPS. Try to get one that has an equipment replacement guarantee. My dad used to work for a computer company. He would go all over the country doing installation and training for businesses. At one credit union, they had a direct lightning strike on the power pole outside the building. The transformer on the pole was blasted into tiny fragments. The UPS in the building did a great job of keeping the surge from entering through the power lines. All of the computers in the building were still running after the strike. There was just one problem. The keyboard cables picked up enough of a charge out of the air, that every computer in the building had a fried keyboard controller chip.
  • I came home once to find that my sister had plugged her surge protector into yet another surge protector ...

    In truth, this is my normal practice ... because of the "A.C. adapters" supplied with things like my speakers, printers, etc., I need more outlet space (physically, not electrically) than one 6-outlet strip provides. So I plug one into the other, and connect the system unit into the second ...

    Having once lost a mobo to a surge, it helps my peace of mind.


  • I've always told people to run around like crazed monkeys and pull the cords to their expensive electronic gear - but lately I've tempered that advice with the caveat that this should only be done when a storm is far away.

    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.

  • by demaria ( 122790 )
    A nice UPS should help a bit, with proper grounding. Not those cheap crappy kind, or surge supressors. I mean APC or other ones that come with $25K guarentees.
  • Most of the stuff out there just protects against lightning induced surges.

    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!


  • I would say that having using the coax protection is probaly not worth the extra money for the surge strip

    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

  • Yes... by tying several knots (ie: ---8---8---8---8---) into a power cord you are basically forming a simple string of single loop inductors [] in series. The brief duration of lightning strikes gives the characteristic voltage spike the properties of high frequency AC. An inductor's impedance (resistance if talking about DC) to AC (and therefore its power dissipation) increases as a function of frequency. Thus, the inductor should offer enough impedance to the voltage spike and burn itself out instead of allowing the voltage spike to travel into your equipment. I wouldn't recommend this method for protecting anything of value. Use a UPS from Best Power or APC and get their equipment replacement guarantee.
  • amendment to 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.
  • by fwc ( 168330 ) on Monday June 25, 2001 @09:50PM (#128331)
    I deal with wireless internet, you know, putting a high gain 2.4ghz antenna on a roof and providing internet to customers via 802.11b stuff.

    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 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...



  • First, there's the business vs. technical solution: The business solution is to make sure it has a surge suppressor with an adequate warranty, and that at any moment adequate backups of everything are offsite AND offline AND redundant.

    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 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.

  • I think this is based on the theory that electricity wants to travel the straightest path possible -- especially high frequency electricity, like lightning.

    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*.

  • I forgot all about the phone line protection actually. I don't use it, becuase on the surge suppressors that I have owned, the telephone protector gives out some sort of EMF that interferes with my radios. (Motorola two-ways and AM radio)

    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)
  • by duffbeer703 ( 177751 ) on Monday June 25, 2001 @07:44PM (#128335)
    1. Backups to tape/cd

    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.
  • I was working as the IT department for a smallish publisher in Albany, NY. We had surge suppressors for all of the desktops, and UPS's for all of the servers. Many computers were hooked up via serial to a proprietary job tracking system, while all of them were on the company LAN. Some where hooked up to an ancient print-sharing device. The company took a major lightening strike one day.

    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:
    • Surge suppressors are useless, basically.
    • You can't protect every device unless you can afford to put everything on a UPS. They're all attached, and all it takes is one thing hooked up to your lan/printer/print sharing device (remember, this was the 80's) to get zapped.
    • As others have stated, have a good back up and disaster recovery plan.
    • And of course, you could always find a way to purposely get hit by lightening, and get it over with. Lightening never strikes the same place twice, right?
  • 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)

  • Actually, it sounds like the building grounds we not/not adaquatly bonded and the path of least resistance was the grounds in the serial/network cables.
  • by jhein ( 194635 ) on Tuesday June 26, 2001 @04:35AM (#128339) Homepage

    Many Hams use products from PolyPhaser [] that are designed to handle a direct strike. They also have information on "What is Lightning?" []

    Also, the ARRL [] has the ARRL Handbook [], 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).

  • (Exception to ammendment #1) Do NOT leave backups in your car if you live in a place where there is crime or criminals might come (heh)

    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...
  • The problem with protecting your system with a flux capacitor, of course, is that if the lightning strike is strong enough ( =/ 1.21 jigawatts) you might end up sending your computer back to the stone age...
  • Maybe you should send them a link if you dig up any good info? ;)

    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!

  • When you say bi-directional Zeners I assume you mean connected cathode to cathode or anode to anode?

    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 was studying for my a+ certification,
    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.
  • A UPS /w insurance and backups is the obvious answer, but they are not very effective if your electrical system has poor grounding. I have seperate grounding for my computer room. I went to the hardware store and got a grounding electrode kit which came with bolts, that and 10 guage wire, I connected it to the already existing ground wire.
  • 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.

    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....)

  • I'm not a subject matter expert on electricity but . .

    It sounds like the serial/parallel/lan was(were) not properly grounded.


  • you can goto home depot, or whatever, and get a little lightning shield that attaches to your fuse box. It provides lightning with the fastest route to the ground protecting all your outlets for about the price of a nice surge suppressor. Then you can use surge suppressors anyway.

    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.

  • Well, my Windows and Free BSD PC's are grounded so well I have potatos growing in the dust in the fans. I use double redunant surge protectors and tie knots in the power cords because we all know lightning travels a straight path and will burn out the cord before striking my PC.

    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.

  • Yes, I've had teh experience of handling a blown-up surge protecter; it was very interesting. I like their guarantee also, although I'd be curious to see their history of making payments -- if my ancient box gets fried, how much would I get payed? I'd guess they pay what it's worth (not much), not what it'd cost to replace it.

    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?

  • What are the chances that the exploding surge protector will save your computer - but start a fire? I'd prefer a fried computer over a fried house.
  • I've got a semi-related question that's been bugging me for the longest time. Don't think I'd ever try this, but...

    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? ;) )

  • Bobbins dont work at all ( i tried fishing spools and a 1 foot diameter tube, allways snap due to snag or something else. I found that a traffic cone works best. Pain in the butt to wrap, but well worth the excitement.

    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.

  • >There is bobbin of wire on the back end of the missile.

    Never thought of that. I sure would like to know how much thrust I would need just to get a good straight launch.

  • I can not repeat the above enough. Where I live in NJ, we get an abnormal amount of strikes (my house has been hit 2 time in 4 years, 1 mile radius has a large percentage of hit, real weird). the big orange cube has all the things you need.

    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.


  • A simple, cheap, effective solution that will work for most home users: Unplug your computer during lightning storms.
  • Yes! DO NOT neglect the modem and/or cable connections. These are wires, and will carry current. About a year ago I lost a pretty nice voice modem during a thunderstorm. The telephone line was not protected, and well, I learned the hard way...
  • Living in the lightening captial of the world means one thing.. you learn to live with strikes.

    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 :)

  • by ez76 ( 322080 )
    I have found it helpful to introduce a flux capacitor in parallel with my surge protector.

    It turns out that this set-up also provides superior protection against Libyan nuclear terrorists and crewcut browbeating types.

  • It doesn't sound very plausible to me, and I've studied double-E (but not lightning).
  • Any spark with enough power to jump across several miles of air isn't going to be stopped by any insulators or suppresors. [sic]
    For all intents and purposes, a Faraday cage stops most anything electromagnetic. A wire and a corona point may be able to stop lightning strikes directly, by creating a space charge around the corona point and eliminating the voltage difference across the crucial last piece of atmosphere. From what I've read, that's enough to direct most lightning strikes elsewhere.

    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?

  • The poster referred to overhand knots (not coils) causing lightning to burn out the cord instead of transmitting the power of a hit to the connected equipment. You are talking about adding inductance, which is useful for choking RFI but has not been shown to be relevant to the issue of lightning.

    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.

  • If you listen to the lightning on an AM radio, you'll hear that the lightning strokes endure for a goodly fraction of a second each. (Use all available information to cross-check your conclusion!)
  • I don't usually go out of my way to rip someone's posting apart, but, dammit, you are presuming to lecture me in my area of expertise (studied, degreed, and professionally experienced).
    All wires have inductance. If current flows through them there is an associated magnetic field. Any change in the level of current causes a change in the magnetic field.
    No shit, Sherlock. Impedance = jL, and you can do a Fourier or LaPlace transform on the input waveform to calculate exactly how the variation in impedance over frequency will affect the response.
    Any change in the original EMF level causes an EMF that fights the change in the original.
    If you'd bothered to read my posting record you'd see that not only do I know that, I can lecture on it at length [].
    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.
    Specifically, it obeys the formulas you can find here []. For an overhand knot of 2 inches diameter (which we can consider to be a one-turn coil), the inductance will be about 0.11 microhenries. If we generously assume that the applied frequency is 1 MHz (unreasonably high, a lightning bolt flickers with characteristic frequencies of a few tens of Hz) the impedance will be less than 1. In other words, any idea of this protecting your equipment against the surge of a lightning strike is bunk.

    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.

    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.
    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 [].

    Now go away or I shall have to taunt you again.

  • by spacefem ( 443435 ) on Tuesday June 26, 2001 @05:08AM (#128365) Homepage
    I like this page [] better for lightning, its map is always up.

    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.
  • With underground cables, there are also benifits:
    1. Aesthetical: no more ugly powerlines
    2. Very few power outages. There is no ice, no wind, no falling trees to take out power lines or phone lines
    3. No chance of electricuting yourself by hitting a power line with a metal ladder, or by climbing a tree
    4. Trees grow in deformed shapes when growing through power lines. This doesn't happen anymore, so there is less of a chance of a tree falling over because the weight is more evenly distributed.
    Lightning does cause more problems, but expensive electronics should be unplugged during a storm anyway! There are no excuses for not doing that.

    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.

  • Lightning does strike the same place twice (I know hirschma was probably kidding, but there are some people who believe this myth). There was a report on the news (Philadelphia, ABC, Channel 6) about a person whose house got hit twice. That's a normal, small, house. There was nothing that would attract lightning. Also, lightning strikes tall skyscrapers almost all the time. Here's a page [] that has info on the Empire State Building. The lightning fact is close to the botton. The building gets struck 100s of times a year, and it acts as a giant lightning rod for the rest of the city.
  • This might be a little off topic, but just as important to consider is power quality also, which includes proper grounding, as mentioned in an earlier post. An UPS can take care of a lot of these problems, but if you have poor power quality, it is very taxing on your UPS. There's a few easy checks you can do with a multi-meter and the outlet you plug your computer into. You can do these checks both with your computer on and off, just use one of the other sockets in the outlets or power strip.

    (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 [] 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...
  • Actually, we found a cheap solution to this problem at the office! (Also saves on wear and tear on the hard drives, etc. and it lowered our energy bills.) :-)

    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......

"If people are good only because they fear punishment, and hope for reward, then we are a sorry lot indeed." -- Albert Einstein