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#1
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Dial up modem problem
"w_tom" wrote in message ... This is deception: I like to tell callers that the modem has acted as a fuse, and saved the rest of their P.C. Lightning has traveled many miles through non-conductive air. Is a silly little 'fuse' going to stop what miles of air did not? Of course not. But basic technology also says a fuse (response time 10 milliseconds) cannot possibly protect from a surge (typically 100 microseconds). No fuse is installed to provide such protection - as demonstrated twice over. First, surge passed through modem's off-hook relay circuit You are starting to grasp the concept then . and other components including motherboard ground plane. well since we are being pedantic here try "heading for the Ground plane" Only then does something fail; typically a modem off-hook relay. built in surge arrestors, Input and Output op-amps, Modem processor, Modem PSU etc etc etc Typical reason for so many computer peripherals damaged - surge entered on AC electric and exited to earth ground via other paths. Damn just when I thought w_tom had grasped the concept. Once again w_tom goes on with his fantasy that Lightning comes in via AC mains and exits via the phone Line. Lets see now applying a little bit of Basic Physics and electrical Theory we have two Lines: Phone Line: No earth on either leg of the cable in fact a very high impedance path to earth via the phone line maybe several kms away. thin relatively high impedance wire with a DC resistance alone running to tens of Ohms (which is why exchange damage is less common - but still occours) AC Mains: typically runs multiple earthed Neutral that is multiple Earth points (in my street about every 25 metres or so) Relativily thick low impedance often multi strand cabling a fraction of an ohm in impedance and with even the Active to Neutral path (via the Transformer) giving a nice low impedance path to earth. hmmmm no prizes for guessing which is the better path to earth here folks ! No damage can occur without both incoming and outgoing path. yep ! One traditional path that causes "No Dialtone Detected" message is incoming on AC electric and outgoing on phone line to earth ground. BS! incoming Lightning coming in via the phone line blowing the living *^&t out of the modem on the way through and exiting the far superior earth on the AC mains Damage that has often been demonstrated by replacing off-hook PNP transistor; making modem work again. In the event of a distant strike maybe if you are lucky (but lets face it who fixes modems nowadays ?) in the event of a near or direct strike ... Forget it your modem is toast. Surge damage is traceable to wires that entered building without a connection to central earth ground. Modem never acts like a fuse nor protected anything. That surge, as taught in primary school science, first must have passed through everything in a complete electric circuit. Many forget primary school science when rationalizing about surge damage. Many say the surge entered on phone line, damaged modem and stopped - Well almost more like Lightning entered modem via phone line and found nice alternative paths to earth via AC mains - also via your PC motherboard if you have an internal modem. But to all intents and purposes since it was safely shunted to (mains) earth at this point and if it did no further damage. it effectively dissapeared from the users view at this point. a direct violation of primary school science. It is that simple. Modem was damaged because surge first took a complete circuit path through that computer - and only then damaged something. well if you are being a pedant it took a complete circuit path through that computer and fried it en route. Richard Unsworth wrote: All I know is that many people I have spoken to while answering technical support lines have suffered blown modems due to a nearby lightning storm. eg. 1. It worked and connected 2. There was thunder and lightning nearby 3. It says 'No dial tone'. And this happened to my pc - I heard just one spectacular bang the April before last - I was about a mile and a half from home. The next day I switched on the pc - dead. Nothing. Having left my diagnostic brain at work, it didn't dawn on me until a local child said 'Have you seen where the lightning blew the paving stone into the road?' This was sixty yards down my street. Yep thats classified as a near strike Result? Modem, motherboard, memory, graphics card, sound card - every component attached directly to the motherboard was dead. w_tom can say all he likes about electrical theory, I dunno why, he has a little trouble grasping basic electrical theory. but experience has shown me that lightning surges down the phone line blow modems up! Yep that right and anyone else in the Comms/Data Comms industry would tell you exactly the same thing. two useful tips: 1) unplug the phone line from your modem/PC when not in use 2)use an external modem for preference - it is no guarantee but at least it keeps lightning that one step further away from your PC After my own experience, I like to tell callers that the modem has acted as a fuse, and saved the rest of their P.C. - they seem to find this reassuring! well while not strictly correct, I know what you mean. Maybe for the sake of the pedants word it as : "your modem acted as a surge arrestor and redirected the Lightning to the Mains earth" Regards Richard Freeman |
#2
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On Mon, 8 Sep 2003 17:28:57 +1000, "Richard Freeman"
put finger to keyboard and composed: Damn just when I thought w_tom had grasped the concept. Once again w_tom goes on with his fantasy that Lightning comes in via AC mains and exits via the phone Line. I was skeptical, too, until I saw it for myself. See this post: http://groups.google.com/groups?selm...&output=gplain - Franc Zabkar -- Please remove one 's' from my address when replying by email. |
#3
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"Franc Zabkar" wrote in message ... On Mon, 8 Sep 2003 17:28:57 +1000, "Richard Freeman" put finger to keyboard and composed: Damn just when I thought w_tom had grasped the concept. Once again w_tom goes on with his fantasy that Lightning comes in via AC mains and exits via the phone Line. I was skeptical, too, until I saw it for myself. See this post: http://groups.google.com/groups?selm...goblue.net. a u&output=gplain Firstly where is this earth on the Telephone line ????? - It does not exist. some (in Australia very few) phone lines have surge arrestors but these are not generally implemented as they have proven to be ineffective in the case of near/Direct strikes. going through your list : Firstly, my friend's neighbour lost his electrical distribution box, so this confirms that the strike came in on the mains. Well Maybe and I have not said it never comes in via Mains just that if it does it is so uncommon that I have not seen it. Reading through the list of damage however suggests that your friend suffered a direct strike in which case : A) all bets are off B) a Lightning strike that has blown the ****e out of a switchboard is barely going to flinch at blowing the ****e out of a MOV C) Equally likely and the more probable scenario is that your friends house was hit and the Lightning followed the path to the best Earth available - that of the MEN Mains Failure of PCtel DAA module (plug-in type for PCChips M585LMR motherboard). Symptom was "NO DIALTONE". Parallel telephone was undamaged. Both phone cables were plugged into a "protected" power board. Plug in module connected to the phone line - still matches the scenario that the strike came in via Phone and exited via Mains The parallel phone most likely rode out the strike. In fact this sounds like a module in a PC if the strike came in via the Mains and exited via the phone line why wasnt the PSU fried ? the more likely scenario is that the strike came in via the phone line and headed for the chassis earth on the PC. (2) Portable telephone base station - shorted 15V zener diode at tip and ring inputs. Powered phone connected to the phone line - still matches the scenario that the strike came in via Phone and exited via Mains (3) Television - shorted rectifier diode, blown fuse, and failures in the +5V regulator, remote sensor, and microcontroller. (4) Two VCRs - CPU and power supply failures. Nasty sounds like a direct strike which also entered via the TV aerial and headed for the earth provided via the double insulated mains - note no phone line involved here (5) Audio unit - CPU failure, P/S OK. Dont know what this was but if double insulated equipment connected to the VCR/TV then Lightning was probably still travelling in via the TV aerial and had not dissipated completely via the VCR or TV Again no phone line connected here (6) Security light - faulty power controller, light dims but won't turn off. Sounds like a direct strike The Light being installed outdoors probably copped a secondary strike not the full Strike - you would have found that one of w_toms surge busters would not have saved this anyway. Also no phone line involved here (7) TV - blown fuse, damage to P/S entered via the TV aerial headed for the AC mains again no phone line involved here Well sounds like your Lightning still mostly obeyed the laws of Physics and entered by unearthed / poorly earthed paths and headed straight for the best earth available that of the AC Mains. as an addendum the mains in this instance probably rode out the strike to a certain degree but in all the cases a path for the lightning to have entered by other than AC mains exsists. Lightning aint Rocket science it obeys the laws of physics - it is just with high energy events such as lightning different laws of physics often come in to play. Lightning seeks a path to the best earth it can find and note here that a single earth stake buried in the ground is more often than not hardly the best earth available the MEN system however used for 240/415V mains distribution however frequently offers a superior earth for Lightning strikes Regards Richard Freeman |
#4
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On Wed, 10 Sep 2003 11:12:46 +1000, "Richard Freeman"
put finger to keyboard and composed: "Franc Zabkar" wrote in message .. . On Mon, 8 Sep 2003 17:28:57 +1000, "Richard Freeman" put finger to keyboard and composed: Damn just when I thought w_tom had grasped the concept. Once again w_tom goes on with his fantasy that Lightning comes in via AC mains and exits via the phone Line. I was skeptical, too, until I saw it for myself. See this post: http://groups.google.com/groups?selm...goblue.net. a u&output=gplain Firstly where is this earth on the Telephone line ????? - It does not exist. In normal circumstances the phone line ground is at the exchange. However, in the case of a lightning strike, the nearest earth is the ground surrounding the cable. In any case, if lightning were to hit the ground, then why would it not dissipate itself in the general mass of earth rather than travelling all the way into the house and onto its local mains earth? Granted, the earth is not homogenous, so a lower potential _could_ exist at the dwelling, but it would seem more likely that an earth strike would not propagate too far away from the epicentre. some (in Australia very few) phone lines have surge arrestors but these are not generally implemented as they have proven to be ineffective in the case of near/Direct strikes. going through your list : Firstly, my friend's neighbour lost his electrical distribution box, so this confirms that the strike came in on the mains. Well Maybe and I have not said it never comes in via Mains just that if it does it is so uncommon that I have not seen it. I have seen it twice at the same dwelling, with similar results. On the second occasion the datapump of an internal 33.6K ISA Rockwell modem was damaged, but the only other problem with the entire PC was a faulty IRQ3 signal on the ISA bus. That's two PCs, neither of which sustained any damage other than a faulty modem DSP/DAA. Reading through the list of damage however suggests that your friend suffered a direct strike in which case : A) all bets are off B) a Lightning strike that has blown the ****e out of a switchboard is barely going to flinch at blowing the ****e out of a MOV C) Equally likely and the more probable scenario is that your friends house was hit and the Lightning followed the path to the best Earth available - that of the MEN Mains Failure of PCtel DAA module (plug-in type for PCChips M585LMR motherboard). Symptom was "NO DIALTONE". Parallel telephone was undamaged. Both phone cables were plugged into a "protected" power board. Plug in module connected to the phone line - still matches the scenario that the strike came in via Phone and exited via Mains The parallel phone most likely rode out the strike. In fact this sounds like a module in a PC if the strike came in via the Mains and exited via the phone line why wasnt the PSU fried ? Clearly the strike struck the mains at some point, so one would intuitively expect that everything connected to the mains would have suffered significant damage, as you say. The fact that the PSU survived suggests that the major part of the potential difference appeared across the DAA of the modem (???). the more likely scenario is that the strike came in via the phone line and headed for the chassis earth on the PC. So we have two strikes, one on the mains and another on the phone line? (2) Portable telephone base station - shorted 15V zener diode at tip and ring inputs. Powered phone connected to the phone line - still matches the scenario that the strike came in via Phone and exited via Mains (3) Television - shorted rectifier diode, blown fuse, and failures in the +5V regulator, remote sensor, and microcontroller. (4) Two VCRs - CPU and power supply failures. Nasty sounds like a direct strike which also entered via the TV aerial and headed for the earth provided via the double insulated mains - note no phone line involved here So now we have three strikes, one on the mains, a second on the phone line, and a third on the aerial? BTW, no tuners or IF stages were damaged. (5) Audio unit - CPU failure, P/S OK. Dont know what this was but if double insulated equipment connected to the VCR/TV then Lightning was probably still travelling in via the TV aerial and had not dissipated completely via the VCR or TV Again no phone line connected here No aerial, no phone line, just mains power. (6) Security light - faulty power controller, light dims but won't turn off. Sounds like a direct strike The Light being installed outdoors probably copped a secondary strike not the full Strike - you would have found that one of w_toms surge busters would not have saved this anyway. Also no phone line involved here (7) TV - blown fuse, damage to P/S entered via the TV aerial headed for the AC mains again no phone line involved here As before, no tuners or IF stages were damaged. Well sounds like your Lightning still mostly obeyed the laws of Physics and entered by unearthed / poorly earthed paths and headed straight for the best earth available that of the AC Mains. as an addendum the mains in this instance probably rode out the strike to a certain degree but in all the cases a path for the lightning to have entered by other than AC mains exsists. Lightning aint Rocket science it obeys the laws of physics - it is just with high energy events such as lightning different laws of physics often come in to play. Lightning seeks a path to the best earth it can find and note here that a single earth stake buried in the ground is more often than not hardly the best earth available the MEN system however used for 240/415V mains distribution however frequently offers a superior earth for Lightning strikes I notice that the one thing that distinguishes a PC from most, if not all the other equipment is the fact that it has an earth conductor. What if this relatively small earth conductor allows the PC to float to the strike potential? Wouldn't the full potential then appear across the modem's DAA rather than the main part of the PC? Regards Richard Freeman I wonder if there is some forensic or metallurgical method of determining the direction of current flow in a lightning strike. - Franc Zabkar -- Please remove one 's' from my address when replying by email. |
#5
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It is almost impossible to try and "scientifically" pick apart how the
energy of a direct ground strike will affect any electrical component. There is just so much energy envolved. I live in an area in the US Midwest that gets many violent storms that contain a large amount of ground strikes. Just about 2 weeks ago, we had a large strike that hit the access post of our phone lines about 30yds from my home. It blew a 3ft deep hole and completely destroyed the phone lines to ours and three other homes. In my home, it only disabled our phone lines and did no damage there, but I have an outside AC/Heat pump and it came in there and completely destroyed my climate control system. No other damage in my house. All the other homes had all their phone outlets burned to a crisp and all phones and at least the modems for their computers were fried. When there is that much energy, wet ground and so many ways for the energy to enter and exit there just aren't enough constants to analize how that energy is going to dissipate itself. There is also no foolproof method of protecting your electronics. I have used good quality UPSs on my electronics for some 5yrs and have been lucky since then. Before that, I used various brands of surge protectors and was constantly having lightning damage. I guess what I am saying is that, yes, the energy will follow the path of least resistance, but with that much energy to dissipate, there are lots of paths it may follow. Ed |
#6
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Are you related to Ed LIGHT? You, both, have a very annoying habit of not
knowing how to quote. It's helpful, in the very least of the sense. SHEESH SEE QUOTE, below. - Ed Medlin stood up at show-n-tell, in , and said: It is almost impossible to try and "scientifically" pick apart how the energy of a direct ground strike will affect any electrical component. There is just so much energy envolved. I live in an area in the US Midwest that gets many violent storms that contain a large amount of ground strikes. Just about 2 weeks ago, we had a large strike that hit the access post of our phone lines about 30yds from my home. It blew a 3ft deep hole and completely destroyed the phone lines to ours and three other homes. In my home, it only disabled our phone lines and did no damage there, but I have an outside AC/Heat pump and it came in there and completely destroyed my climate control system. No other damage in my house. All the other homes had all their phone outlets burned to a crisp and all phones and at least the modems for their computers were fried. When there is that much energy, wet ground and so many ways for the energy to enter and exit there just aren't enough constants to analize how that energy is going to dissipate itself. There is also no foolproof method of protecting your electronics. I have used good quality UPSs on my electronics for some 5yrs and have been lucky since then. Before that, I used various brands of surge protectors and was constantly having lightning damage. I guess what I am saying is that, yes, the energy will follow the path of least resistance, but with that much energy to dissipate, there are lots of paths it may follow. Ed -- Strontium "It's no surprise, to me. I am my own worst enemy. `Cause every now, and then, I kick the livin' **** `outta me." - Lit |
#7
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--------snipped for brevity------------
Firstly where is this earth on the Telephone line ????? - It does not exist. In normal circumstances the phone line ground is at the exchange. However, in the case of a lightning strike, the nearest earth is the ground surrounding the cable. In any case, if lightning were to hit the ground, then why would it not dissipate itself in the general mass of earth rather than travelling all the way into the house and onto its local mains earth? Granted, the earth is not homogenous, so a lower potential _could_ exist at the dwelling, but it would seem more likely that an earth strike would not propagate too far away from the epicentre. Firstly A single earth point is usually a relatively poor earth often providing up to tens of Ohms Resistance to 'earth' when Lightning hits say an earth stake that earth point typically rises to 50,000V or more above nominal Earth as a result. There have been many cases where a Lightning strike to the ground has blown through the insulation of a cable and travelled through it to a better ground however this usually also causes physical damage to the phone cable. Secondly the Phone line is not earthed back at the exchange it is in fact floating above ground potential - It needs to be as it is a Balanced Circuit. Thirdly the DC resistance alone of a phone line is fairly high typically being in the order of a hundred or more Ohms especially when compared to the mains. In other words any earth on a typical Phone line is nowhere near as effective as the earth provided by the MEN AC distribution System. some (in Australia very few) phone lines have surge arrestors but these are not generally implemented as they have proven to be ineffective in the case of near/Direct strikes. going through your list : Firstly, my friend's neighbour lost his electrical distribution box, so this confirms that the strike came in on the mains. Well Maybe and I have not said it never comes in via Mains just that if it does it is so uncommon that I have not seen it. I have seen it twice at the same dwelling, with similar results. On the second occasion the datapump of an internal 33.6K ISA Rockwell modem was damaged, but the only other problem with the entire PC was a faulty IRQ3 signal on the ISA bus. That's two PCs, neither of which sustained any damage other than a faulty modem DSP/DAA. So the damage was to the modem both times! this was likely to have come via AC mains because ? Reading through the list of damage however suggests that your friend suffered a direct strike in which case : A) all bets are off B) a Lightning strike that has blown the ****e out of a switchboard is barely going to flinch at blowing the ****e out of a MOV C) Equally likely and the more probable scenario is that your friends house was hit and the Lightning followed the path to the best Earth available - that of the MEN Mains Failure of PCtel DAA module (plug-in type for PCChips M585LMR motherboard). Symptom was "NO DIALTONE". Parallel telephone was undamaged. Both phone cables were plugged into a "protected" power board. Plug in module connected to the phone line - still matches the scenario that the strike came in via Phone and exited via Mains The parallel phone most likely rode out the strike. In fact this sounds like a module in a PC if the strike came in via the Mains and exited via the phone line why wasnt the PSU fried ? Clearly the strike struck the mains at some point, so one would intuitively expect that everything connected to the mains would have suffered significant damage, as you say. The fact that the PSU survived suggests that the major part of the potential difference appeared across the DAA of the modem (???). most likely it came in via the floating phone line and headed for the MEN earth - it was possibley even sufficent to cause localised EPR (Earth Potential Rise) however given the relatively low impedance House wiring (against the Higher impedance phone line for eg ) and the relatively high impedance path from the phone line to the Mains earth most of the voltage for the strike would have appeared between the phone line and the mains earth. the more likely scenario is that the strike came in via the phone line and headed for the chassis earth on the PC. So we have two strikes, one on the mains and another on the phone line? Nope one strike most likely direct to the house/Aerial/Phone line and a ****e load of current heading for the MEN earth inducing all sorts of voltages in and around the house wiring. (2) Portable telephone base station - shorted 15V zener diode at tip and ring inputs. Powered phone connected to the phone line - still matches the scenario that the strike came in via Phone and exited via Mains (3) Television - shorted rectifier diode, blown fuse, and failures in the +5V regulator, remote sensor, and microcontroller. (4) Two VCRs - CPU and power supply failures. Nasty sounds like a direct strike which also entered via the TV aerial and headed for the earth provided via the double insulated mains - note no phone line involved here So now we have three strikes, one on the mains, a second on the phone line, and a third on the aerial? Nope still only one direct Strike and a bunch of induced current in various bits of metal a single Lightning strike can and often does induce fairly high currents/voltages through nearby wiring especially in a Direct (or even near) Strike. One main strike though. bear in mind that w_tom s 'whole house protection' would most likely not have saved anything in this strike either. BTW, no tuners or IF stages were damaged. (5) Audio unit - CPU failure, P/S OK. Dont know what this was but if double insulated equipment connected to the VCR/TV then Lightning was probably still travelling in via the TV aerial and had not dissipated completely via the VCR or TV Again no phone line connected here No aerial, no phone line, just mains power. still have no idea what this is - speaker cables or signal cables ? (6) Security light - faulty power controller, light dims but won't turn off. Sounds like a direct strike The Light being installed outdoors probably copped a secondary strike not the full Strike - you would have found that one of w_toms surge busters would not have saved this anyway. Also no phone line involved here (7) TV - blown fuse, damage to P/S entered via the TV aerial headed for the AC mains again no phone line involved here As before, no tuners or IF stages were damaged. Double insulated telly though most likely so that the highest impedance part of the path to earth (and hence the higher voltage across components) would have been through the PSU. The TV most likely even had some surge supression for thhe Aerial which would have excacerbated this failure. Well sounds like your Lightning still mostly obeyed the laws of Physics and entered by unearthed / poorly earthed paths and headed straight for the best earth available that of the AC Mains. as an addendum the mains in this instance probably rode out the strike to a certain degree but in all the cases a path for the lightning to have entered by other than AC mains exsists. Lightning aint Rocket science it obeys the laws of physics - it is just with high energy events such as lightning different laws of physics often come in to play. Lightning seeks a path to the best earth it can find and note here that a single earth stake buried in the ground is more often than not hardly the best earth available the MEN system however used for 240/415V mains distribution however frequently offers a superior earth for Lightning strikes I notice that the one thing that distinguishes a PC from most, if not all the other equipment is the fact that it has an earth conductor. What if this relatively small earth conductor allows the PC to float to the strike potential? Wouldn't the full potential then appear across the modem's DAA rather than the main part of the PC? The earth conducter to a PC is going to still going to have a resistance of a fraction of an ohm against over 1000's of ohms to earth via the Phone line Regards Richard Freeman I wonder if there is some forensic or metallurgical method of determining the direction of current flow in a lightning strike. why ? just think about it compare the two earths - MEN AC Mains earth = fraction of an Ohm to Earth - Directly connected to earth stakes at not one but Several Places with a minimum wire size of 2.5mm square (O.k with typically 2 m of 1.5mm square cable for the IEC power lead). Phone Line = floating above Earth potential with a Maximum wire size of 0.28mm Square not connected to an earth anywhere. Which sounds like the better earth to you ? If you where Lightning where would you head ? It is not rocket science it is just fairly basic electrical theory - very simple physics. Dont be mislead by the wilfully ignorant especially those who seem to have a vested interest in selling 'whole house protection'. Regards Richard Freeman |
#8
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First, Richard is in Australia where he has little (probably
no) experience with effective protection. For example, telephone companies in North America install 'whole house' protectors at each customer's premise interface with a connection to earth. Those effective 'whole house' protectors make a connection from each phone wire to earth ground. Surge on a NA phone line is earthed before it can enter the building. Richard would not know about this because Australian telcos typically do not provide effective surge protectors - for free. IOW in Australia, surges incoming on phone line are possible - just one more path that makes surge damage even that more likely. Just another reason why Richard would speculate that surge protection is not possible. How would he know? He does not have any. If he has no protectors, then how would Richard know that properly sized and earthed surge protectors are effective? Second, phone lines at the exchange are earthed. Earthing (via surge protectors) is located to be distant from the switching computer - up to 50 meters separation. That separation between surge protector and transistor is part of the surge protection 'system'. Every wire entering that switching center must first have a connection to central earth ground - either by direct connection or via surge protector. Why does Richard also not know this? Why is he so critical and yet does not even know basic wiring and earthing inside a telco switching center? Earthing is so effective that, for example, emergency response operators don't remove headsets during thunderstorms. No surge entering on phone lines. This is old technology proven long before WWII. Richard is speculating without even having learned what has been proven generations ago - before WWII. Effective surge protection is about earthing the surge. So effective that surge damage is considered a human failure. Third, if Richard knew basics of surge protection, then he would know that DC resistance is irrelevant. Wire impedance - not resistance - is the important number. If he knew his 'stuff', then he would identify the component that keeps an AC mains surge from finding earth ground via a modem. It only takes a multimeter. A direct connection exists between some pins on modem ICs and one AC electric wire. A direct connection that makes modem damage from AC electric possible. So where is this 'isolator' that keeps an AC mains surge from finding modem? Richard tells us that AC mains cannot connect a surge through modem. Then Richard can tell us which component isolates modem from AC mains surges? Richard also does not know the energy content of a lightning strike. He only speculates. Alan Taylor of the US Forestry Service demonstrated the energy content. In more than 95% of lightning strikes to trees, the strike left no perceptible indication that a strike had even occurred. That's right. Lightning strikes typically are not high energy events. Many are such low energy events as to not even leave indication. Lightning is a high power event; not high energy event. Richard should enlighten us with numbers of his high energy lightning strike. Therein lies another problem with his speculations. He provides no numbers to go along with his no experience. In the meantime, even the US Army demonstrates in training manuals what is required to earth a direct lightning strike. They require 10 AWG (2.5 mm dia) wires to connect lightning rod to earth. That thin wire connects the direct lightning strike from air terminal to earth without damage - because energy content in lightning is that small. Just more numbers. Lightning is easily earthed without damage. The art of surge protection is earthing - to keep the surge outside of the building. One path for destructive surge that is permitted inside a building: incoming on AC electric, destructively through mode, and outgoing to earth ground on phone line. Damage because one incoming wire - AC electric - was not earthed (via 'whole house' surge protector) before entering building. Effective surge protection is about earthing every incoming wire before it can enter the building. Once inside a building, the surge will find numerous, destructive paths to earth ground. Surge protectors are only as effective as their earth ground. Richard Freeman is invited to describe the component that keeps an AC mains surge from finding path through modem. Richard is invited to put up some energy numbers for a CG lightning strike. Richard is invited to contradict US Army Training Manual 5-690; to prove that earth direct lightning strikes cannot be earthed using only 10 AWG (25 amp) wires. Richard is invited to put some scientific numbers up with his speculations. If he cannot provide the numbers, then he is only promoting junk science reasoning. In the meantime, a common destructive path for modems is incoming on AC electric and outgoing to earth ground via phone line. A path proven too often by tracing the surge and replacing damaged components in that path. It called experience that is in agreement with underlying theory, research papers, and industry professionals. Richard Freeman wrote: --------snipped for brevity------------ Firstly where is this earth on the Telephone line ????? - It does not exist. In normal circumstances the phone line ground is at the exchange. However, in the case of a lightning strike, the nearest earth is the ground surrounding the cable. In any case, if lightning were to hit the ground, then why would it not dissipate itself in the general mass of earth rather than travelling all the way into the house and onto its local mains earth? Granted, the earth is not homogenous, so a lower potential _could_ exist at the dwelling, but it would seem more likely that an earth strike would not propagate too far away from the epicentre. Firstly A single earth point is usually a relatively poor earth often providing up to tens of Ohms Resistance to 'earth' when Lightning hits say an earth stake that earth point typically rises to 50,000V or more above nominal Earth as a result. There have been many cases where a Lightning strike to the ground has blown through the insulation of a cable and travelled through it to a better ground however this usually also causes physical damage to the phone cable. Secondly the Phone line is not earthed back at the exchange it is in fact floating above ground potential - It needs to be as it is a Balanced Circuit. Thirdly the DC resistance alone of a phone line is fairly high typically being in the order of a hundred or more Ohms especially when compared to the mains. In other words any earth on a typical Phone line is nowhere near as effective as the earth provided by the MEN AC distribution System. some (in Australia very few) phone lines have surge arrestors but these are not generally implemented as they have proven to be ineffective in the case of near/Direct strikes. going through your list : Firstly, my friend's neighbour lost his electrical distribution box, so this confirms that the strike came in on the mains. Well Maybe and I have not said it never comes in via Mains just that if it does it is so uncommon that I have not seen it. I have seen it twice at the same dwelling, with similar results. On the second occasion the datapump of an internal 33.6K ISA Rockwell modem was damaged, but the only other problem with the entire PC was a faulty IRQ3 signal on the ISA bus. That's two PCs, neither of which sustained any damage other than a faulty modem DSP/DAA. So the damage was to the modem both times! this was likely to have come via AC mains because ? Reading through the list of damage however suggests that your friend suffered a direct strike in which case : A) all bets are off B) a Lightning strike that has blown the ****e out of a switchboard is barely going to flinch at blowing the ****e out of a MOV C) Equally likely and the more probable scenario is that your friends house was hit and the Lightning followed the path to the best Earth available - that of the MEN Mains Failure of PCtel DAA module (plug-in type for PCChips M585LMR motherboard). Symptom was "NO DIALTONE". Parallel telephone was undamaged. Both phone cables were plugged into a "protected" power board. Plug in module connected to the phone line - still matches the scenario that the strike came in via Phone and exited via Mains The parallel phone most likely rode out the strike. In fact this sounds like a module in a PC if the strike came in via the Mains and exited via the phone line why wasnt the PSU fried ? Clearly the strike struck the mains at some point, so one would intuitively expect that everything connected to the mains would have suffered significant damage, as you say. The fact that the PSU survived suggests that the major part of the potential difference appeared across the DAA of the modem (???). most likely it came in via the floating phone line and headed for the MEN earth - it was possibley even sufficent to cause localised EPR (Earth Potential Rise) however given the relatively low impedance House wiring (against the Higher impedance phone line for eg ) and the relatively high impedance path from the phone line to the Mains earth most of the voltage for the strike would have appeared between the phone line and the mains earth. the more likely scenario is that the strike came in via the phone line and headed for the chassis earth on the PC. So we have two strikes, one on the mains and another on the phone line? Nope one strike most likely direct to the house/Aerial/Phone line and a ****e load of current heading for the MEN earth inducing all sorts of voltages in and around the house wiring. (2) Portable telephone base station - shorted 15V zener diode at tip and ring inputs. Powered phone connected to the phone line - still matches the scenario that the strike came in via Phone and exited via Mains (3) Television - shorted rectifier diode, blown fuse, and failures in the +5V regulator, remote sensor, and microcontroller. (4) Two VCRs - CPU and power supply failures. Nasty sounds like a direct strike which also entered via the TV aerial and headed for the earth provided via the double insulated mains - note no phone line involved here So now we have three strikes, one on the mains, a second on the phone line, and a third on the aerial? Nope still only one direct Strike and a bunch of induced current in various bits of metal a single Lightning strike can and often does induce fairly high currents/voltages through nearby wiring especially in a Direct (or even near) Strike. One main strike though. bear in mind that w_tom s 'whole house protection' would most likely not have saved anything in this strike either. BTW, no tuners or IF stages were damaged. (5) Audio unit - CPU failure, P/S OK. Dont know what this was but if double insulated equipment connected to the VCR/TV then Lightning was probably still travelling in via the TV aerial and had not dissipated completely via the VCR or TV Again no phone line connected here No aerial, no phone line, just mains power. still have no idea what this is - speaker cables or signal cables ? (6) Security light - faulty power controller, light dims but won't turn off. Sounds like a direct strike The Light being installed outdoors probably copped a secondary strike not the full Strike - you would have found that one of w_toms surge busters would not have saved this anyway. Also no phone line involved here (7) TV - blown fuse, damage to P/S entered via the TV aerial headed for the AC mains again no phone line involved here As before, no tuners or IF stages were damaged. Double insulated telly though most likely so that the highest impedance part of the path to earth (and hence the higher voltage across components) would have been through the PSU. The TV most likely even had some surge supression for thhe Aerial which would have excacerbated this failure. Well sounds like your Lightning still mostly obeyed the laws of Physics and entered by unearthed / poorly earthed paths and headed straight for the best earth available that of the AC Mains. as an addendum the mains in this instance probably rode out the strike to a certain degree but in all the cases a path for the lightning to have entered by other than AC mains exsists. Lightning aint Rocket science it obeys the laws of physics - it is just with high energy events such as lightning different laws of physics often come in to play. Lightning seeks a path to the best earth it can find and note here that a single earth stake buried in the ground is more often than not hardly the best earth available the MEN system however used for 240/415V mains distribution however frequently offers a superior earth for Lightning strikes I notice that the one thing that distinguishes a PC from most, if not all the other equipment is the fact that it has an earth conductor. What if this relatively small earth conductor allows the PC to float to the strike potential? Wouldn't the full potential then appear across the modem's DAA rather than the main part of the PC? The earth conducter to a PC is going to still going to have a resistance of a fraction of an ohm against over 1000's of ohms to earth via the Phone line Regards Richard Freeman I wonder if there is some forensic or metallurgical method of determining the direction of current flow in a lightning strike. why ? just think about it compare the two earths - MEN AC Mains earth = fraction of an Ohm to Earth - Directly connected to earth stakes at not one but Several Places with a minimum wire size of 2.5mm square (O.k with typically 2 m of 1.5mm square cable for the IEC power lead). Phone Line = floating above Earth potential with a Maximum wire size of 0.28mm Square not connected to an earth anywhere. Which sounds like the better earth to you ? If you where Lightning where would you head ? It is not rocket science it is just fairly basic electrical theory - very simple physics. Dont be mislead by the wilfully ignorant especially those who seem to have a vested interest in selling 'whole house protection'. Regards Richard Freeman |
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Those effective 'whole house' protectors
make a connection from each phone wire to earth ground. Surge on a NA phone line is earthed before it can enter the building. One comment here...this also depends on the 'IN' house wiring being done correctly or is undamaged.....in older homes where the lines have been butchered this does not hold true... especially on the NID on the side of the house, seen them knocked off with lawnmowers etc,,....just hanging there by the wires, ground ripped off. "w_tom" wrote in message ... First, Richard is in Australia where he has little (probably no) experience with effective protection. For example, telephone companies in North America install 'whole house' protectors at each customer's premise interface with a connection to earth. Those effective 'whole house' protectors make a connection from each phone wire to earth ground. Surge on a NA phone line is earthed before it can enter the building. Richard would not know about this because Australian telcos typically do not provide effective surge protectors - for free. IOW in Australia, surges incoming on phone line are possible - just one more path that makes surge damage even that more likely. Just another reason why Richard would speculate that surge protection is not possible. How would he know? He does not have any. If he has no protectors, then how would Richard know that properly sized and earthed surge protectors are effective? Second, phone lines at the exchange are earthed. Earthing (via surge protectors) is located to be distant from the switching computer - up to 50 meters separation. That separation between surge protector and transistor is part of the surge protection 'system'. Every wire entering that switching center must first have a connection to central earth ground - either by direct connection or via surge protector. Why does Richard also not know this? Why is he so critical and yet does not even know basic wiring and earthing inside a telco switching center? Earthing is so effective that, for example, emergency response operators don't remove headsets during thunderstorms. No surge entering on phone lines. This is old technology proven long before WWII. Richard is speculating without even having learned what has been proven generations ago - before WWII. Effective surge protection is about earthing the surge. So effective that surge damage is considered a human failure. Third, if Richard knew basics of surge protection, then he would know that DC resistance is irrelevant. Wire impedance - not resistance - is the important number. If he knew his 'stuff', then he would identify the component that keeps an AC mains surge from finding earth ground via a modem. It only takes a multimeter. A direct connection exists between some pins on modem ICs and one AC electric wire. A direct connection that makes modem damage from AC electric possible. So where is this 'isolator' that keeps an AC mains surge from finding modem? Richard tells us that AC mains cannot connect a surge through modem. Then Richard can tell us which component isolates modem from AC mains surges? Richard also does not know the energy content of a lightning strike. He only speculates. Alan Taylor of the US Forestry Service demonstrated the energy content. In more than 95% of lightning strikes to trees, the strike left no perceptible indication that a strike had even occurred. That's right. Lightning strikes typically are not high energy events. Many are such low energy events as to not even leave indication. Lightning is a high power event; not high energy event. Richard should enlighten us with numbers of his high energy lightning strike. Therein lies another problem with his speculations. He provides no numbers to go along with his no experience. In the meantime, even the US Army demonstrates in training manuals what is required to earth a direct lightning strike. They require 10 AWG (2.5 mm dia) wires to connect lightning rod to earth. That thin wire connects the direct lightning strike from air terminal to earth without damage - because energy content in lightning is that small. Just more numbers. Lightning is easily earthed without damage. The art of surge protection is earthing - to keep the surge outside of the building. One path for destructive surge that is permitted inside a building: incoming on AC electric, destructively through mode, and outgoing to earth ground on phone line. Damage because one incoming wire - AC electric - was not earthed (via 'whole house' surge protector) before entering building. Effective surge protection is about earthing every incoming wire before it can enter the building. Once inside a building, the surge will find numerous, destructive paths to earth ground. Surge protectors are only as effective as their earth ground. Richard Freeman is invited to describe the component that keeps an AC mains surge from finding path through modem. Richard is invited to put up some energy numbers for a CG lightning strike. Richard is invited to contradict US Army Training Manual 5-690; to prove that earth direct lightning strikes cannot be earthed using only 10 AWG (25 amp) wires. Richard is invited to put some scientific numbers up with his speculations. If he cannot provide the numbers, then he is only promoting junk science reasoning. In the meantime, a common destructive path for modems is incoming on AC electric and outgoing to earth ground via phone line. A path proven too often by tracing the surge and replacing damaged components in that path. It called experience that is in agreement with underlying theory, research papers, and industry professionals. Richard Freeman wrote: --------snipped for brevity------------ Firstly where is this earth on the Telephone line ????? - It does not exist. In normal circumstances the phone line ground is at the exchange. However, in the case of a lightning strike, the nearest earth is the ground surrounding the cable. In any case, if lightning were to hit the ground, then why would it not dissipate itself in the general mass of earth rather than travelling all the way into the house and onto its local mains earth? Granted, the earth is not homogenous, so a lower potential _could_ exist at the dwelling, but it would seem more likely that an earth strike would not propagate too far away from the epicentre. Firstly A single earth point is usually a relatively poor earth often providing up to tens of Ohms Resistance to 'earth' when Lightning hits say an earth stake that earth point typically rises to 50,000V or more above nominal Earth as a result. There have been many cases where a Lightning strike to the ground has blown through the insulation of a cable and travelled through it to a better ground however this usually also causes physical damage to the phone cable. Secondly the Phone line is not earthed back at the exchange it is in fact floating above ground potential - It needs to be as it is a Balanced Circuit. Thirdly the DC resistance alone of a phone line is fairly high typically being in the order of a hundred or more Ohms especially when compared to the mains. In other words any earth on a typical Phone line is nowhere near as effective as the earth provided by the MEN AC distribution System. some (in Australia very few) phone lines have surge arrestors but these are not generally implemented as they have proven to be ineffective in the case of near/Direct strikes. going through your list : Firstly, my friend's neighbour lost his electrical distribution box, so this confirms that the strike came in on the mains. Well Maybe and I have not said it never comes in via Mains just that if it does it is so uncommon that I have not seen it. I have seen it twice at the same dwelling, with similar results. On the second occasion the datapump of an internal 33.6K ISA Rockwell modem was damaged, but the only other problem with the entire PC was a faulty IRQ3 signal on the ISA bus. That's two PCs, neither of which sustained any damage other than a faulty modem DSP/DAA. So the damage was to the modem both times! this was likely to have come via AC mains because ? Reading through the list of damage however suggests that your friend suffered a direct strike in which case : A) all bets are off B) a Lightning strike that has blown the ****e out of a switchboard is barely going to flinch at blowing the ****e out of a MOV C) Equally likely and the more probable scenario is that your friends house was hit and the Lightning followed the path to the best Earth available - that of the MEN Mains Failure of PCtel DAA module (plug-in type for PCChips M585LMR motherboard). Symptom was "NO DIALTONE". Parallel telephone was undamaged. Both phone cables were plugged into a "protected" power board. Plug in module connected to the phone line - still matches the scenario that the strike came in via Phone and exited via Mains The parallel phone most likely rode out the strike. In fact this sounds like a module in a PC if the strike came in via the Mains and exited via the phone line why wasnt the PSU fried ? Clearly the strike struck the mains at some point, so one would intuitively expect that everything connected to the mains would have suffered significant damage, as you say. The fact that the PSU survived suggests that the major part of the potential difference appeared across the DAA of the modem (???). most likely it came in via the floating phone line and headed for the MEN earth - it was possibley even sufficent to cause localised EPR (Earth Potential Rise) however given the relatively low impedance House wiring (against the Higher impedance phone line for eg ) and the relatively high impedance path from the phone line to the Mains earth most of the voltage for the strike would have appeared between the phone line and the mains earth. the more likely scenario is that the strike came in via the phone line and headed for the chassis earth on the PC. So we have two strikes, one on the mains and another on the phone line? Nope one strike most likely direct to the house/Aerial/Phone line and a ****e load of current heading for the MEN earth inducing all sorts of voltages in and around the house wiring. (2) Portable telephone base station - shorted 15V zener diode at tip and ring inputs. Powered phone connected to the phone line - still matches the scenario that the strike came in via Phone and exited via Mains (3) Television - shorted rectifier diode, blown fuse, and failures in the +5V regulator, remote sensor, and microcontroller. (4) Two VCRs - CPU and power supply failures. Nasty sounds like a direct strike which also entered via the TV aerial and headed for the earth provided via the double insulated mains - note no phone line involved here So now we have three strikes, one on the mains, a second on the phone line, and a third on the aerial? Nope still only one direct Strike and a bunch of induced current in various bits of metal a single Lightning strike can and often does induce fairly high currents/voltages through nearby wiring especially in a Direct (or even near) Strike. One main strike though. bear in mind that w_tom s 'whole house protection' would most likely not have saved anything in this strike either. BTW, no tuners or IF stages were damaged. (5) Audio unit - CPU failure, P/S OK. Dont know what this was but if double insulated equipment connected to the VCR/TV then Lightning was probably still travelling in via the TV aerial and had not dissipated completely via the VCR or TV Again no phone line connected here No aerial, no phone line, just mains power. still have no idea what this is - speaker cables or signal cables ? (6) Security light - faulty power controller, light dims but won't turn off. Sounds like a direct strike The Light being installed outdoors probably copped a secondary strike not the full Strike - you would have found that one of w_toms surge busters would not have saved this anyway. Also no phone line involved here (7) TV - blown fuse, damage to P/S entered via the TV aerial headed for the AC mains again no phone line involved here As before, no tuners or IF stages were damaged. Double insulated telly though most likely so that the highest impedance part of the path to earth (and hence the higher voltage across components) would have been through the PSU. The TV most likely even had some surge supression for thhe Aerial which would have excacerbated this failure. Well sounds like your Lightning still mostly obeyed the laws of Physics and entered by unearthed / poorly earthed paths and headed straight for the best earth available that of the AC Mains. as an addendum the mains in this instance probably rode out the strike to a certain degree but in all the cases a path for the lightning to have entered by other than AC mains exsists. Lightning aint Rocket science it obeys the laws of physics - it is just with high energy events such as lightning different laws of physics often come in to play. Lightning seeks a path to the best earth it can find and note here that a single earth stake buried in the ground is more often than not hardly the best earth available the MEN system however used for 240/415V mains distribution however frequently offers a superior earth for Lightning strikes I notice that the one thing that distinguishes a PC from most, if not all the other equipment is the fact that it has an earth conductor. What if this relatively small earth conductor allows the PC to float to the strike potential? Wouldn't the full potential then appear across the modem's DAA rather than the main part of the PC? The earth conducter to a PC is going to still going to have a resistance of a fraction of an ohm against over 1000's of ohms to earth via the Phone line Regards Richard Freeman I wonder if there is some forensic or metallurgical method of determining the direction of current flow in a lightning strike. why ? just think about it compare the two earths - MEN AC Mains earth = fraction of an Ohm to Earth - Directly connected to earth stakes at not one but Several Places with a minimum wire size of 2.5mm square (O.k with typically 2 m of 1.5mm square cable for the IEC power lead). Phone Line = floating above Earth potential with a Maximum wire size of 0.28mm Square not connected to an earth anywhere. Which sounds like the better earth to you ? If you where Lightning where would you head ? It is not rocket science it is just fairly basic electrical theory - very simple physics. Dont be mislead by the wilfully ignorant especially those who seem to have a vested interest in selling 'whole house protection'. Regards Richard Freeman |
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Ahhh more Ignorance from the annonymous w_tom
"w_tom" wrote in message ... First, Richard is in Australia where he has little (probably no) experience with effective protection. So is Frank Zabkar or did you fail to notice ? For example, telephone companies in North America install 'whole house' protectors at each customer's premise interface with a connection to earth. Those effective 'whole house' protectors make a connection from each phone wire to earth ground. Surge on a NA phone line is earthed before it can enter the building. Provided : A) The surge arrestor does not evaporate or burn out - whichthey will and do in Direct/Near strikes B) The earth consists of more than a Single Earth stake Richard would not know about this because Australian telcos typically do not provide effective surge protectors - for free. IOW in Australia, surges incoming on phone line are possible - just one more path that makes surge damage even that more likely. Just another reason why Richard would speculate that surge protection is not possible. Wrong the reason I know Telco Surge protection is no defense against near or direct strikes is that I have seen Time and Time again surge protection literally blown off the distribution frame (where it has been installed) and equipment on those lines dead following near or direct strikes. How would he know? He does not have any. If he has no protectors, then how would Richard know that properly sized and earthed surge protectors are effective? how big then I have certainly seen 1 Joule MOVs destroyed - yes with short Earth leads to the mains/Switchboard earth stake Second, phone lines at the exchange are earthed. Earthing (via surge protectors) is located to be distant from the switching computer - up to 50 meters separation. That separation between surge protector and transistor is part of the surge protection 'system'. Every wire entering that switching center must first have a connection to central earth ground - either by direct connection or via surge protector. Why does Richard also not know this? Why is he so critical and yet does not even know basic wiring and earthing inside a telco switching center? Well w_tom is showing his lack of knowledge about how exchanges are installed by feeding more erronous information Telephone exchanges have very extensive earthing systems - this is true All metal work in the exchange is tied to earth Exchanges are usually fed by underground cables and enter through an earthed metal sheath the underground conduits near the exchange are earthed back to the exchange earth Exchange Buildings have extensive Lightning protection Surge protection for individual lines is on the LI board - But this is only effective for distant strikes however taking the other precautions ensures that most strikes are distant - in the event of direct strikes damage can and does still occour although this is more common on RCMs or RIMs (which do have Surge arrestors connected directly to earth stakes ie with less than 1M of wire) which do suffer damage during direct or near strikes which usually also completely destroys the surge arrestors ( should really be called diverters). Earthing is so effective that, for example, emergency response operators don't remove headsets during thunderstorms. No surge entering on phone lines. This is old technology proven long before WWII. Richard is speculating without even having learned what has been proven generations ago - before WWII. Effective surge protection is about earthing the surge. So effective that surge damage is considered a human failure. emergency operators used to be sited in exchanges for all the reasons listed above or in buildings in city areas where the phone lines firstly terminate on a PABX or local switch (which is going to effectively isolate the operator from any Lightning injury ) however nowadays emergency operators are in call centres which are fed by Fibre optics systems which for some very strange reason do not seem to have the problems that normal phone lines do they are however usually connected to mains though often with no surge protection other than what is provided by the equipment maunfacurer yet very rarely suffer outages let alone injury I wonder why ? Third, if Richard knew basics of surge protection, then he would know that DC resistance is irrelevant. Wire impedance - not resistance - is the important number. perhaps w_tom can explain how a single strand 0.28mm square wire is going to exhibit a lower impedance than a multi-strand 2.5mm square wire oops it does not not under any circumstance maybe if w_tom knew basic Electrical theory and basic Physics he would not make these sorts of errors. I quoted DC resistance as it is readily measurable in the examples I used the impedance will be higher I admit but the imedance of the Mains wiring is still going to be a fraction of the impedance of the phone line. Note here that w_tom top posts so that people cannot take the original statement in context and therefore see how ridiculous w_toms argument is If he knew his 'stuff', then he would identify the component that keeps an AC mains surge from finding earth ground via a modem. It only takes a multimeter. A direct connection exists between some pins on modem ICs and one AC electric wire. It does ???? Which modem IC pins would they be ??? thats funny all ( I have found 6 so far ) the modems I have here (and a number are made in america ) are double insulated - THERE IS NO DIRECT CONNECTION BETWEEN ANY PINS ON ANY IC IN THE MODEM AND AC MAINS ! w_tom is merely showing his ignorance again - Modems nowadays are built for an international market and the easiest way of dealing with all the power variations is to power the modem from a (double insulated) plugpack even older modems which I used to Repair (that right component level repair) which did have metal cases had no direct connection between active or Neutral and the internal Electronics they did however have a mains earth connected to the internal Electronics and Lightning damage was typically between the Line interface and the Mains earth with other damage scattered around the modem depending on how close the strike was. Modern modems that are double insulated are effectively earthed via the Serial cable back to the PC (every PC I have seen has an insulated case - with the exception of Laptops) which is why damage can and often does include damage to the DSP in the modem and sometimes the serial interface in the PC. A direct connection that makes modem damage from AC electric possible. So where is this 'isolator' that keeps an AC mains surge from finding modem? Richard tells us that AC mains cannot connect a surge through modem. Then Richard can tell us which component isolates modem from AC mains surges? It is a very simple device in use since before World War 1 called a Transformer another very simple device which has been in use for well over 100 years is called a capacitor Richard also does not know the energy content of a lightning strike. He only speculates. Alan Taylor of the US Forestry Service demonstrated the energy content. In more than 95% of lightning strikes to trees, the strike left no perceptible indication that a strike had even occurred. That's right. Hmmm lets see a non conductive (wooden tree trunk does not conduct electricity - Lightning) but the conductive water wetting the Tree trunk does - gee what a surprise. This still does not explain the Trees that are blown to pieces by Lightning Strikes though. Actually it does not seem to explain the damage that this 'harmless' Lightning does do. Lightning strikes typically are not high energy events. Many are such low energy events as to not even leave indication. Lightning is a high power event; not high energy event. Richard should enlighten us with numbers of his high energy lightning strike. Therein lies another problem with his speculations. He provides no numbers to go along with his no experience. I have given the Numbers before but w_tom has ignored them as they are too inconvenient to his arguments but once more for the dummy : Lightning does vary in strength but is Typically between 1,000,000,000 and 10,000,000,000 Joules (thanks Professor Martin A. Uman,Professor of Electrical and Computer Engineering at the University of Florida, Gainsville) In the meantime, even the US Army demonstrates in training manuals what is required to earth a direct lightning strike. They require 10 AWG (2.5 mm dia) wires to connect lightning rod to earth. That thin wire connects the direct lightning strike from air terminal to earth without damage - because energy content in lightning is that small. Just more numbers. oh thats funny sothe MEN earth is adequate ? Lightning is easily earthed without damage. The art of surge protection is earthing - to keep the surge outside of the building. True cant disagree here One path for destructive surge that is permitted inside a building: incoming on AC electric, destructively through mode, and outgoing to earth ground on phone line. Damage because one incoming wire - AC electric - was not earthed (via 'whole house' surge protector) before entering building. a fairly rare event however. The low imedance nature of the Mains distribution System and the superior nature of the Earth provide via MEN power distribution means that the MEN AC mains absorbs most of the few (very few) strikes that avoid the Neutral or Earth wires in the power reticulation System - NB Telephone distribution cables DO NOT have this Earth and hence (even when buried underground) are far more susceptible to damage and surges from Lightning. Effective surge protection is about earthing every incoming wire before it can enter the building. Once inside a building, the surge will find numerous, destructive paths to earth ground. Surge protectors are only as effective as their earth ground. True however Surge protectors are also limited by their ability to withstand High Currents - typically in the order of 4500 Amps or more for 100uSec with a tail averaging 500-1000A for another 0.25 Sec Richard Freeman is invited to describe the component that keeps an AC mains surge from finding path through modem. wrong way around again the surge comes from the high impedance phone line and seeks Mains (MEN) earth w_tom has still not explained in any truthful manner how Lightning is effectively earthed on a phone line (0.28mm square single strand copper copper wire ,No direct Earth connection etc) but not on an MEN power distribution System which has one Wire tied directly to an Earth stake at not one place but every Switchboard it enters (on a typical street around near where I live the Neutral is tied to earth approximately 30Metres or so and all connected together with at least 6mm square multi strand Copper cable. Richard is invited to put up some energy numbers for a CG lightning strike. Richard is invited to contradict US Army Training Manual 5-690; to prove that earth direct lightning strikes cannot be earthed using only 10 AWG (25 amp) wires. Richard is invited to put some scientific numbers up with his speculations. If he cannot provide the numbers, then he is only promoting junk science reasoning. Thats funny w_tom is accusing me of saying what he is claiming namely that Lightning on a MEN mains distribution System cannot be effectively earthed by Low impedance cabling connected to multiple earths - I have not and have never made this claim ! what I have said is that MOVs in the event of a near or direct strike cannot be expected to handle shunting the strike effectively to earth this has been proved time and time and time again - not usually on AC mains where the MEN system effectively absorbs and shunts most of the strike to earth - but on Telephone and Data Lines where the copper is floating above Earth Potential and is not earthed at any point (except for the ill fated 'surge arrestors'). I have also not made the claim that in the event of a Direct strike no damage ever occours via surges on the AC cabling - what I have said is that Destructive Lightning surges on mains cabling is very very Rare and that the most common pathe for Lightning damage is : In from unearthed or poorly earthed sources such as aerials, phone lines and Data lines and out to the MEN Mains earth - note with single point Earthing as often erronously used for Lightning protection any effective earthing must be tied back to the far more effective MEN Earth as a single earth stake in the event of a Lightning strike will exhibit an EPR (I see w_toms favourite polyphasor site refers to it as GPR) in excess of 50,000V In the meantime, a common destructive path for modems is incoming on AC electric and outgoing to earth ground via phone line. A path proven too often by tracing the surge and replacing damaged components in that path. It called experience that is in agreement with underlying theory, research papers, and industry professionals. Arse about face as would be expected from someone who has shown little grasp of basic Physics, or Basic Electrical Theory, very little knowledge of MEN power distribution, effective Earthing Techniques and almost no knowledge of Telephony or Data communications. His claims go in the face of experience that is in agreement with Electrical Theory, Basic Physics Reasearch Papers and Industry Professionals (in the IT&T Industry). I shall summarise my Arguments here to keep the facts that w_tom avoids straight : Most Lightning damage enters via the Phone line, Aerials or other unearthed wiring and exits to the MEN Mains earth. Surge arrestors in the event of a near or direct strike if they are doing their job do not usually last long enough to be effective. Surge arrestors on AC mains do usually outlast those on phone lines mainly because the MEN power distribution system does a pretty good job of absorbing Lightning strikes already. Finally : The best and most effective way ofprotecting your Computer in the event of a lightning strike is firstly use an external modem - this helps keep lightning at arms length from the computer and secondly physically disconnect the modem from the phone when not in use especially if there is any chance of a Thunderstorm (powering it off is not enough). As a final note the name I sign with is my real name as I know that everything I say is accurate however w_tom chooses to remain anonymous (I wonder why is he scared of being sued by those who took his advice and still suffered Lightning damage ?) Regards Richard Freeman |
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