Here in New York City (Manhattan) where I live, I usually use a laptop computer running on an AC adapter, and get online via a dial-up modem (phone line plugged into computer's built-in modem).
When it's merely raining outside, it's usually of no concern to me. But when there's lightning or thunder, I quickly get offline, turn off the computer, and literally unplug the AC adapter from the outlet, and unplug the phone line from the computer.
This is done to avoid the possibility of the AC adapter or the modem suffering damage from a voltage spike carried through either the AC power line or the phone line (because of a lightning strike).
Does all this sound sensible to you, or am I being overly/unneccesarily cautious?
Very wise. A couple years back I had a modem fried by a nearby lightning strike and I'm grateful that's all that was fried. These days if I even think I hear thunder I pull all the plugs and go read a good book. My suggestion, anyway...
Your precautions are very sensible. Not only is the computer, modem and power supply at risk, if you happen to be near a ground connection, your body is at some risk, also.
However, there is a simple precaution you can take that makes it much safer to use your computer during a rain storm. Get a filtered, surge suppressed power strip that has both receptacles and phone line sockets. The surge suppressers help limit the voltage peaks between any of the incoming power lines, which protects the supply, but also limits the peak voltage between the phone lines and the power ground, protecting both the modem and you from anything but a very close strike. I still wouldn't use it in the bath tub, though.
Here is an example of one without a low pass filter (just surge suppressers):
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And a bigger unit that includes the RFI filter (that improves the operation of the surge suppression a bit).
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I am not endorsing these particular products, just using them as examples of what I am talking about.
The greatest danger is from your modem. Surges coming in through telephone lines can do quite a bit of damage. In fact, I've had desktops almost completely smoked via the modem. Fried the motherboard, video, AND drives (both CD and HDD). Spared the RAM and the power supply and not much else. And yes, it is absolutely certain that it was through the telephone line, not through the power line. Surge suppressors and uninterruptible power supplies MAY protect from telephone line surges well enough, or they may not. After having a computer smoked and having seen my neighbor's computer smoked in the same way I stopped using internal modems altogether, but of course external modems are seldom used with a laptop. Your computer power supply will possibly protect your laptop well enough from power surges with sacrificial diodes in the rectifier circuit, but it's a better bet to unplug and run off the battery. I'm sure you don't want to even have to buy a new AC supply for your laptop. Those can be expensive, although Radio Shack carries AC supplies that MAY be enough for your computer (mine actually requires more amperage than the RS model can supply on startup, and if the battery is down the thing won't boot).
Turning it off would help. but _very_ little. Unplugging it would be the correct thing to do. I"ve had more analog modems fried by lightning (4) then cable modems (2) but you can see, it happens. Personally I don't bother with unplugging the cable modem as Brighthouse really does not have a problem replaceing them with no charge.
If you live in a densely populated city and all these cables come through underground cables there is very little risk for damage from lightning.
The high voltages from a lightning must then travel long distances through underground cable systems, and the power is distributed among thousands of end users connections.
There is probably also good protection systems in place to protect against overvoltage conditions.
Earlier I lived in a small old house on top of a mountain, with electricity and phone lines coming through the air, wires on poles.
Now that was a risky place to live at during lightning storms!
And there was often lightning hits even on clear days, without any warning signals in the weather at all.
I have had my telephone practically explode a few feet from my head, and I have had lots of equipment destroyed. Mainly modems and tv sets but also other stuff.
Then I installed some protection components, spark gap devices, on both the electricity and phone lines. Where the lines enter the house and inside the house, close to the computer and tv set too. I also increased the lightning protection for the house with lightning rods and lots of wires in the ground around the house to absorb the power better.
That helped a lot, and I had no equipment destroyed for those 6 years I lived there when I had the protection components installed.
Compared to my house on a mountain you are very well protected in a densely populated city with underground cable systems for electricity, phone lines, cable tv and cable internet.
A lot of people have a situation somewhere between these two extremes, big city or mountain top, and may want to take necessary precautions.
The easiest way to add protection to vital equipment is to put all of it on an extension cord with multiple outlets and add protection circuits to that extension cord system. Make sure that both phone connection and electricity connection are protected where they enter that extension cord system.
Sounds sensible to me. You could also try getting a good surge protector. Then you won't have to unplug everything. I would make sure that the phone cable also runs through the surge protector or unplug it.
About a year ago, we had a thunder storm where a bolt of lightening actually struck our back garden. The PC in the office was protected by a UPS / filter, but the DSL connection through the phone line and the external modem/router weren't protected. The lightening fried the modem and the network card in the PC! Fortunately the rest of the PC was ok.
Now, the PC is protected by a UPS, and the modem/router's phone connection is filtered through a surge protection device.
A wide variety of good responses and outright myths. Some just post answers without even providing a single reasons why. Those posters are particularly insidious and typically respond with insults.
Turning something off will not help. Destructive surges were not stopped or absorbed by 3 miles of air. Why then will millimeters inside a switch do what miles of air could not?
In the early days of ham radio, equipment would suffer lightning damage. Antenna lead was disconnected and even put inside a mason jar. Damage finally stopped when the antenna lead was connected to earth ground. They only rediscovered what Ben Franklin demonstrated in 1752. Lightning seeks earth ground. If not earthed before entering a building, then lightning will seek earth ground, destructively through appliances.
Some will claim that a plug-in protector would help. Again, plug-in protector will stop or block what miles of air could not? So very quietly, those plug-in manufacturers forget to mention they don't even claim to protect from that destructive type of surge. Obviously. No dedicated earth ground. They just let others assume all surges are the same type.
Industry professionals demonstrate how protection is installed as it was proven before WWII on the Empire State Building.
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Two structures each with their own single point earth ground. Any wire entering each structure first makes a connection to that earth ground. Connection either by a hardwire or via a surge protector. Notice what an effective surge protector does. Makes a temporary and short connection to earth ground during a surge.
Also notice the buried phone wire in that figure. Even underground wires must first connect to that single point earth ground. Yes even underground wires will carry destructive surges inside a building.
So what can you do? Protection is a building wide solution. However if your circuit breaker box is 'earthed' (connected) to building steel, then it already has an excellent single point ground. Breaker box then gets a 'whole house' protector so that surges entering on AC mains are immediately earthed long before they can get to your computer. Most destructive surges - especially to modems and portable phone base stations - are incoming on AC electric.
Same applies to phone line. But phone line already has an effective protector provided free by the telco because 'whole house' protectors are so effective and so inexpensive. Cable company is also required to bond to earth ground where cable enters the building. Cable requires no surge protector because cable can make a direct (hardwired) connection to earth ground.
All electronics contains internal protection. Anything that is effective on an appliance power cord would already be inside the appliance. But that internal protection assumes destructive transients are earthed before entering a building. Earthed transients will not overwhelm protection already installed in appliances. Again, protection that has been proven repeated in virtually every town for so many decades. Protection that does not use plug-in protectors.
Do not fall for urban myths that a UPS or power strip will filter or stop surges. Again, a 1 inch component will stop what miles of sky could not? Of course not. A UPS will stop or filter a surge? Franklin did not stop or absorb lightning. He shunted (diverted, connected) an electrical transient to earth so that it did not seek earth ground via a church steeple. Effective protection inside telephone switching centers, 911 emergency response centers, and even in grocery stores do same.
A telephone switching center connected to overhead wires everywhere in town does not unplug during thunderstorms. And yet that is what your are being told. They simply connect every incoming wire to single point earth ground where wires enter the building. Protection that is best located 50 meters from computers.
The plug-in protector does not even claim to protect from the destructive type of surge. It claims to protect from surges that don't typically exist. Myth purveyors then assume protector protects from all kinds of surges - not knowing that different types of surges exist.
Plug-in manufacturer encourages others to play word games as if it was technical fact. Surge protector and surge protection are same? No. All protection 'systems' require surge protection - earth ground. Only some incoming utilities require a surge protector to connect to surge protection. A surge protector is only as effective as its earth ground. Plug-in protector manufacturers even avoid discussing earth ground. Telling the 'whole truth' would only hurt profits. Effective protection is a 'whole house' protector. Therefore internal appliance protection will not be overwhelmed. A surge protector is only as effective as its earth ground.
Recommended is a 'whole house' protector at AC ma> Here in New York City (Manhattan) where I live, I usually use a laptop
There are 3 potential failures here: o Data-corruption from power failure
---- for a laptop this risk is removed (usefully :-) o Modem is damaged thro telco system
---- not impossible even in NYC, not uncommon in rural or elsewhere
---- for an onboard modem you 1) lose your modem or 2) lose the laptop
---- both of which involve downtime & expense o Computer is damaged through mains system
---- lightning will happily hit buildings, then run thro mains systems
It's not uncommon for lightning some distance away to cause line-drops, as well as major power dips (brownouts/sags) and surges. Computer PSU are switched-mode PSUs so tolerant of large variations in power, but that is not a guarantee where lightning is concerned.
Telephone cables often run outside a building, along walls, which can be interesting re picking up voltage from lightning or attraction.
When lightning appears to have gone, remember it can still strike some distance from the originating storm - even in blue-sky. That is how most people are struck by lightning, and potentially buildings, power poles etc.
If your power comes in thro a pole transformer, and same for telco, then local lightning can pose a serious risk to both power & telephone services. Colleague lost the corner of their tiny sub-let warehouse last year due to a lightning strike - what wasn't burnt was electrically damaged.
So whilst it may seem old-fashiooned, it's not a bad idea. Certainly unplugging the telco connection. In the UK the master telco socket has a GDT, gas discharge tube, but if lightning is close they're a bit useless. If something nearby is hit, the surge protectors can save a modem etc, but a direct or very close strike will generally take out anything re energy.
--
Dorothy Bradbury
www.stores.ebay.co.uk/panaflofan for quiet Panaflo fans & other items
www.dorothybradbury.co.uk (free delivery)
How about 'Cable Broadband ' delivery...Obviously a 'Telephone' is not used..But cable is !...So do I need to turn my Cable Modem off as well ..or not..?..
An adjacent surge protector contains a device that does not stop surges. It simply shunts all wires together during that surge. A surge shunted from one wire to all others goes where? Remember, the destructive surge seeks earth ground. It now has more paths to find earth ground, destructively, via the adjacent computer. What kind of protection is that adjacent protector? Ineffective.
Telcos prefer their protectors located 50 meters from a $multimillion switching computer. Protectors adjacent to the computer might only shunt the surge to earth through that computer. Many cable companies now add additional restrictions to how cable is installed. Connection from cable to earth ground must be significantly shorter than connection from same point to TV or cable modem. Why? Effective protector is distant from transistor and adjacent to earth ground.
A surge protector is only as effective as its earth ground. Effective protectors make a 'less than 10 foot' connection to earth. No plug-in protector will make that connection. Just another reason why plug-in protectors are so ineffective. Just another reason why plug-in protector manufacturers avoid all discussion about earthing. They don't claim to protect from that type of surge.
Your example of an adjacent power strip protector works IF destructive surges are normal mode. Destructive surges are longitudinal mode. That means a surge shunted by the power strip will seek many paths back to earth ground - including destructively through a computer modem. The resulting error message may be 'No Dialtone Detected'.
Damage you demonstrate inside a modem is classic of a surge that enters on AC electric. Remember primary school science. First electricity must flow through everything in that circuit. Only later does something fail. A complete circuit from cloud to earth is fully energized. Then the modem fails. Classic modem damage is a surge that enters on AC electric, passes through modem, then outgoing to earth ground on phone line. This surge often damages the modem's DAA section - the phone wire side of modem.
Many assume surges act like ocean waves. The surge destroys the first component encountered? Of course not. Surge first travels through everything in the circuit. Only then does something fail. A failed DAA section does not say where surge comes from. But many will tell us the surge ignored a telco installed 'whole house' protector to enter modem via that phone line. Why does surge completely ignore the phone line 'whole house' protector? Because many don't even know the protector exists.
Surge enters on utility wire that has no 'whole house' protector - AC electric. It then leaves (makes a complete electrical circuit) by leaving - going to earth ground - via phone line.
How does the phone line surge completely ignore a telephone company installed 'whole house' protector? It must to enter on phone line.
Your theory is good IF surge is normal mode. Manufacturer's specifications claim to protect from normal mode transients. Problem is that destructive surges are not normal mode. So manufacturer forgets to mention two things:
1) plug-in protectors don't provide protection from the typically destructive type of surge and 2) earth ground. By forgetting to mention other types of surges, they have promoted protection myths. Many then *assume* it protects from all types of surges.
Destructive surges must be earthed before entering a building. Then protection internal to all household appliances will not be overwhelmed.
Let's see. We spend $15 or $50 to protect only one appliance. What protects smoke detectors, intercom, dishwasher, etc? Effective 'whole house' protector costs about $1 per protected appliance. Furthermore it provides protection from all types of surges. Plug-in protectors don't make such claims.
Your example only demonstrate that plug-in protectors work as speced. Your example forgets to discuss the type of surge that typically damages electronics. All appliances contain any protection that is effective adjacent to appliance. Internal protection that requires 'whole house' protection on every utility wire where that wire enters building.
Why are plug-in protectors often so undersized - have so few joules? They are not really selling effective protection. Why waste good money on more parts - more joules? Profit - not protection - is the agenda with plug-in protectors.
The odds of a lightning strike doing any damage in a densely populated region such as Manhattan are astronomically slim. If I lived in that area I wouldn't worry about it. There are so many tall buildings in Manhattan to attract lightning and the majority of them probably have lightning rods on them.
The situation in a rural area is different. I once had some electronic equipment fried by a nearby lightning strike a few years ago in a suburban Philadelphia home.
If you don't understand normal and longitudinal mode, then you do not even have first year engineering knowledge. People with insufficient knowledge that can promote myths about plug-in protectors. If you think that power strip surge protector provides more than normal mode protection, then simply cite the manufacturer's spec. I state this knowing full well there is no such spec. Manufacturer does not even claim to provide that protection. Why then would you? You are confusing normal mode with longitudinal mode.
Lets put numbers to your previous example. Lets say a small (100 amp) transient approaches your power strip surge protector. Let's say the wall receptacle connects to breaker box with 50 feet of 12 AWG wire inside walls. Now let's assume your power strip protector shunts all 100 amps to wall receptacle safety ground. That 50 foot wire is less than 0.2 ohms resistance. But to the transient, it is something on the order of 130 ohms impedance. Basic engineering. Wire has impedance. 100 amps times 130 ohms puts the power strip protector at something less than 13,000 volts. Will that
13,000 volts try to obtain earth ground via 50' safety ground wire? Of course not. It will seek many other paths to earth ground. One destructive path is via computer modem and telephone wire.
So what has that power strip surge protector done? Again, nothing complex here. The concepts only require first year engineering. That power strip has shunted the 100 amp surge from black hot wire onto all other wires. It has contributed to damage of an adjacent and powered off computer.
I don't understand why you have so much difficulty with the concept; assuming you have engineering training. These numbers only demonstrate what has been well understood for generations. Surge protection has always been about earthing a surge before it can enter a building. Need I again cite how telephone switching centers are constructed so as to not suffer surge damage. Need I again cite the legendary application notes of Polyphaser? What advertisement? Anyone familiar with real surge protector knows this name as an industry benchmark:
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Or maybe the National Institute of Science and Technology might help. They are not advertising. Their figure is used to demonstrate how a fax machine is protected or may be damaged. Again 'whole house' protector and the all so critical single point earth ground:
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Yes, you made a good case for normal mode protecti> I feel like I am discussing loudspeaker cables with an audio hi fidelity
A good surge protector contains one or more of these components:
A spark gap device, also called ComGap, which allows overvoltage, charge, to jump to the earth connection.
A VDR which is slower than the Comgap, but it lowers the voltage to zero, which protects the Comgap, this is needed if we are talking about a mains wire, because mains delivers current until the mains cycle reaches the zero crossing, and this current hurts the Comgap device.
A Comgap needs to be used in series with a resistor, a big mass type resistor, value 20 Ohm or so. The VDR is used in parallell with this Comgap-resistor combination.
To make the protection better one can use small coils in the signal/mains way, after the comgap. The coils stop fast voltage changes and make the comgaps take the charge instead.
The comgaps and the VDR:s need to have the right voltage, 450Volt for a
240Volt mains wire, a 140Volt for the phone line.
It doesn't hurt the computer and other devices if the voltage is raised a thousand volts for a short moment, as long as all connections to it are raised together. So the surge protector only has to keep all connections at fairly the same voltage, even if they all are raised momentarily. What really hurts the equipment is if one of the connections moves far away from the other connections, because then there is a surge inside that piece of equipment, burning some component to pieces.
That is why the extension with outlets protected by a surge protector works. It creates a subsystem which is kept together at virtually the same potential for all connections to that subsystem.
When a modem is hurt by the lightning it is because the mains connection to it and the phone connection to it are pulled apart by thousands of volts, and that creates a damaging surge inside the modem.
If both the mains and phone line connections to the modem first have to pass through a protector box, where they are prevented from moving apart too much, voltage-wise, the modem is protected.
I feel like I am discussing loudspeaker cables with an audio hi fidelity enthusiast.
You obviously do not understand what I am saying, but you have a lot to say about special modes, earth connections and special brands, which doesn't make sense from a scientific point of view.
You do not have an education in electronics, but you have a brain filled with blurb from advertisements.
On Monday 20 September 2004 07:37 pm, nospam256K did deign to grace us with the following:
An apartment I was living in once took a direct hit. It's pure dumb luck that I had unplugged the modem - it took out the answering machine and a desk phone. It also blew out a couple of exit lights - the manager said there was a total of about $7,000 damage from that one strike.
So, if it's actively lightninging, you're not being overly/unneccesarily cautious to unplug stuff. It also took out the on/off transistor in the TV, so the remote wouldn't turn it off any more. I had to get up and walk to the TV, until I got it fixed, of course. I took it to the shop, and asked how much a diagnosis was, which was about $35.00, and the repair would have been about $85.00, so I just asked the tech to mark the transistor so I could replace it myself. I had to rearrange the leads on a plastic 2222, but it fixed it. :-)
A lot of useful information in these links, but you still need an education in electronics to fully understand that information.
Like Henri Poincare said: Facts are just the building blocks of science, you need to know how to build them together, you need models and theories, that is real science.
"Ground Potential Rise (GPR)", is used a lot on the Polyphaser web site. If you understood what it means you would not write about "sitting ON earth", as you did in your earlier message, because no point can be exactly "on earth" during a thunder storm. All points are moving voltage-wise, so you have to choose a suitable moving point and use it in a proper way.
As I stated earlier, the important thing is not to keep everything exactly at earth potential, because that is impossible, read about GPR, the important thing is to prevent different parts of the system from moving too far apart voltage-wise. And that is what we use spark gaps and other devices for. This can be done for a whole building or for subsystems within a building.
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