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#21
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Are you selling lightening protection? You have so much faith. Tell us
about ground loops. "w_tom" wrote in message ... Effective protection costs so little. For example, go to Home Depot or Radio Shack from something called a grounding block for incoming cable TV line. It costs less than $2 retail. Connect this grounding block less than 10 feet using 12 AWG or heavier wire. Now the CATV line is fully surge protected. Yes, the cable line requires no surge protector. A surge protector is nothing more than a temporary connection to earth ground. BUT the ground block has already made that protection connection using a 12 AWG wire. Where is the big cost? Unfortunately we still don't build new homes for transistor safety. So effective protection often must be installed as an after thought. Sometimes, this means the incoming cable - improperly installed - must be moved. Now we are talking big bucks; and only because humans were the reasons for failure. I recently had this discussion with some cable installer who keep saying, "Is that what they were saying", or "That's right. They said something about that". Every incoming wire must connect to single point earth ground. That connection is either via a protector or hard wire. The telephone company even installs a 'whole house' protector .... for free. But again, it is only as effective as the earth ground provided by the home builder. I don't see where all this expense is. Many waste big bucks on plug in protectors that (quietly) don't even claim to provide effective protection. The missing information is that damning. IOW those expensive protectors also are ineffective solutions. The less expensive 'whole house' protector connected 'less than 10 feet' to protection is the less expensive and more effective solution. Which wire is most often struck? Wire highest on telephone pole. AC electric. This is a direct strike to the computer inside the house IF effective 'whole house' protectors do not connect to that all so essential single point earth ground. "It depends" is a discussion about the human who did or did not install effective protection - and what it takes to correct that mistake. There is no reason for any electronics to be damaged by surges. And some locations make protection far more essential. The need for earthed protection varies even with geology AND can vary significantly even within the same town. notritenoteri wrote: You're right 5 years with no damage doesn't prove anything but it does point to the fact that the cost to take extraordinary precautions to protect against rare events is probably not worth it. On the other hand spending money on the best possible lightening protection for a radio antenna tower may be worthwhile. Your claim that protection is easily installed is somewhat misleading. The facts are "it depends" |
#22
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Ground loops is why surge protection must be the single
point ground. Problems created by ground loop (the damaged fax machine) is demonstrated by the NIST figure and previously cited discussion in: http://www.epri-peac.com/tutorials/sol01tut.html Which would you believe? Lies promoted by half truths on retail store shelves? Or fact demonstrated by telephone and 911 emergency operators who never need remove headsets during every lightning storm. Effective protection is demonstrated by telephone switching computers that connect to overhead wires everywhere in town. Its not called faith. Its called facts. 1) Demonstrated by theory and 2) proven by example virtually everywhere in the civilized world. Posted was well understood and repeatedly proven even before WWII. One classic myths is that surge protectors operate too slow. Even the GDTs that routinely provided surge protection before WWII and that were much slower were also fast enough for surge protection. These are facts know to those who understood how surge protectors work. 'Surge protector works too slow' is but another myth. Obviously a myth because it is routinely promoted without numbers. One must believe such myths only on faith. notritenoteri wrote: Are you selling lightening protection? You have so much faith. Tell us about ground loops. |
#23
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w_tom wrote: Effective protection costs so little. For example, go to Home Depot or Radio Shack from something called a grounding block for incoming cable TV line. It costs less than $2 retail. Connect this grounding block less than 10 feet using 12 AWG or heavier wire. Now the CATV line is fully surge protected. Yes, the cable line requires no surge protector. A surge protector is nothing more than a temporary connection to earth ground. BUT the ground block has already made that protection connection using a 12 AWG wire. Where is the big cost? I think you'll find - if you check really carefully - that the grounding block merely ensures that the incoming cable ground connection is, in fact, connected to a good ground close to it's final destination. Surge protectors otoh make sure that the *signal* (or hot wire in the case of AC cables) can short rapidly to ground in the event of an over-voltage. It's done by connecting a MOV (metal oxide varistor) from signal/hot to ground. At normal operating voltages, this device is an open-circuit but in the case of a voltage surge rapidly transforms to a short-circuit shunting the surge to ground. Having a decent ground alone helps but if you think the grounding block you refer to means your CATV is "fully" surge protected, you are sadly mislead. |
#24
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Power loss will not damage hardware. 'Power loss causes
damage' is often suggested without underlying technical fact. Why? Underlying facts were never learned. Sometimes, a power loss is preceded by a surge. Then a human may blame power loss rather than the undetected surge. The surge caused both hardware damage and power loss. Human instead blamed power loss. Computers using obsolete technology such as FAT file systems can (in rare cases) erase data previously saved on disk drive. But power loss does not cause the damage. Damage is caused by a well known and long since eliminated problem that still exists in FAT file systems. Systems with critical data on FAT filesystems should use a UPS - to protect that data. If 'power loss' causes hardware damage, then 'power off' also causes hardware damage. Most parts in a computer (ie hard drive) don't know the difference between 'power loss' and 'power shutdown'. They power down normally no matter how power is removed. BTW, how does a UPS protect from power outages? First power is completely lost for a short time. Then the UPS switches over to battery. IOW one spec essential for a computer power supply is its Hold Up Time. Computer power supply must keep outputting voltage while no power is incoming - while UPS is trying to decide that power is lost. No problem IF a power supply contains functions that were defacto 30 years ago AND that are required in Intel specs. But again, just another reason why intermittent power loss should not cause damage. UPS claims no protection from the typically destructive surges. If it did, then numbers could be provided for that specification. Anything that provides protection at a computer is already inside that computer. The plug-in UPS can even give lightning other destructive paths through the computer. Yes, an adjacent UPS could even contribute to hardware damage of adjacent electronics. Instead, the plug-in UPS manufacturer provided no numerical specs for each type of transient AND avoids all discussion about earthing. Plug-in UPS provides no effective hardware protection when the manufacturer does not even provide numerical specs for that ability. Another function that is already in a minimally acceptable power supply. When line voltage dips so low that incandescent bulbs are less than 40% intensity: even Intel specs state the power supply under full load must startup and run as if line voltage was normal. IOW a UPS for moderate voltage sags is sometimes a cure for a defective power supply. That is but another reason why a minimally acceptable power supply retails for $65. Also why those who buy $25 power supply suddenly discover they need the plug-in UPS. Bottom line - the plug-in UPS is only for data protection. Hardware protection is located elsewhere such as inside a minimally acceptable power supply, and in the 'whole house' protection system. How resilient are computers? Well this plug-in 120 volt UPS in battery backup mode outputs two 200 volt square waves with a 270 volt spike while under minimum load. Is that 270 volt spike, et al destructive? Yes, it can be destructive to some small electric motors. But this UPS is 'computer grade'. That means UPS is for devices that are more resilient - such as computers. Where is the transient protection? Inside the power supply so that even a UPS in battery backup mode will not damage the computer. Leythos wrote: I agree and have to point out one thing here in case people become confused: In most homes the typical problem is cause by loss of power for any length of time - this causes the computer to reset in the middle of anything it was/is doing. This is more likely to happen than a spike or sag in line power. A UPS, even a cheap 750VA unit, will protect your computer from power outages, sags and some increases in line voltage that happen within the amount of time that the unit can respond. If you want lightning protection you're looking at something other than a home user UPS. If you combine lightning protection at the breaker panel (where this is a good earth ground - at least there's suppose to be one) with a home user UPS, then you've got the protection you need for about 99% of anything you will run into. I have a lot of APC Smart-UPS 2200VA units around the country and love them, but at $800 they are not something that most home users are going to buy. The short of this discussion is that the small UPS units people purchase for their home computers are not likely to protect them or survive a lightning surge, but, since those are rare for most of us, the UPS will save you when the power sags, surges, or goes out completely - which is much more likely to happen. |
#25
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Consult industry professionals: if a center conductor
connects to coax shield using an MOV, well, MOVs have too much capacitance. They would short out (attenuate) high frequency signals. Even the telco protector does not use MOVs due to too much capacitance on lower frequency phone lines. First, MOV shorting center conductor to coax shield is enough to suspect insufficient technical knowledge. MOV capacitance and impedance problems created by that capacitance are well understood - which is why MOVs are not acceptable for CATV, DSL, ISDN, satellite receivers, etc. Second, leakages from the center conductor to shield means that the destructive surge - if surge even gets to the center conductor - is leaked to shield and earthed by the ground block. Again, earth ground - not a surge protector - defines the quality and effectiveness of protection. Problem with being 'sadly mislead' is that I know why that MOV cannot be located as was posted. WoofWoof wrote: I think you'll find - if you check really carefully - that the grounding block merely ensures that the incoming cable ground connection is, in fact, connected to a good ground close to it's final destination. Surge protectors otoh make sure that the *signal* (or hot wire in the case of AC cables) can short rapidly to ground in the event of an over-voltage. It's done by connecting a MOV (metal oxide varistor) from signal/hot to ground. At normal operating voltages, this device is an open-circuit but in the case of a voltage surge rapidly transforms to a short-circuit shunting the surge to ground. Having a decent ground alone helps but if you think the grounding block you refer to means your CATV is "fully" surge protected, you are sadly mislead. |
#26
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My house was built this year, so its earthing should be up to 1990
national building codes. But how can I be sure the builder did it correctly? I don't think this is anything that the local building inspector can test. I doubt he could tell the difference between a 10-inch grounding rod and one that was driven 20 feet into the ground, if he even inspects this feature at all. How can I tell if my house is earthed correctly? On Fri, 14 Jan 2005 14:28:21 -0500, w_tom wrote: Plug in protectors claim to protect from one type of surge. Do some punching. As one arm swings out, the other withdrawals. That 1-2 punching is an example of a surge that typically does not do damage. Now instead punch with both left and right arms simultaneously. That is the common mode surge that typically damages electronics. Lightning seeks earth ground. It comes down any and all 'arms', passes through punching bag, and exits out other side of punching bag. The plug-in protector does not stop, block, or absorb such destructive surges. IOW it does not sit between surge and the electronics - even though they hope you will assume that. And effective protector connects earlier where wires enter the building so that the 'surge down all wires simultaneously' all find the same earth ground. Lightning in 1752 found earth ground destructively via a church steeple. Franklin simply gave lightning a better path to earth. Lightning is the 'all arms moving forward at the same time" type of surge. You don't stop, block, or filter what miles of sky could not even stop. You 'shunt' lightning to earth ground. That is also what the 'whole house' protector does. It provides lightning with a short path to earth ground. You are surprised how small the Cutler Hammer unit is. It need not be large because it does not stop, block, or absorb the energy. Wire is also not massive because it too carry massive electrical energy and does not try to stop or block it. A surge protector is nothing more than a wire. A wire that conducts only during the rare and short transient. It can be small because the transient is only in microseconds. In a parallel example, try to push a common nail into wood. You cannot. It takes the force of a backhoe to drive that nail. However, we hit that nail with only a 20 oz hammer. Does the human arm have same energy as the backhoe? Of course not. People often confuse energy with power. The hammer has low energy but high power. Lightning has low energy but high power. The protector need not be monstrous because 1) it does not stop or absorb the energy, and 2) the energy is not as massive as urban myths portray. Too many only 'feel' that a lightning strike is high energy. The electrical circuit is best demonstrated by an NIST figure used in an example from: http://www.epri-peac.com/tutorials/sol01tut.html They demonstrate why a fax machine was damaged. Notice that the phone line was not 'earthed' less than 10 feet to the same single point ground as AC electric. Telephone line protector is inside the box labeled NID. The 'whole house' protector is located where 'Arrestor' is labeled. Notice that the destructive surge goes through Arrestor, then to earth ground. Since it need not pass through fax machine to get earth ground, then an AC electric surge does not damage fax machine. All electronic appliances contain effective protection. Anything that is going to work on the end of a power cord (those grossly overpriced plug-in protectors) is already inside electronics - as even required by industry standards. But we worry that internal electronics protection might be overwhelmed. So we install a 'whole house' protector on every incoming utility wire - to same earth ground. Demonstrated in various posts is the AC electric 'whole house' protector (such as the Cutler Hammer), the telco provided protector, and a ground block for cable wire (no protector required). All are only as effective as that earth ground. Now about earthing. Engineered discussed this in two discussions in the newsgroup misc.rural entitled: Storm and Lightning damage in the country 28 Jul 2002 Lightning Nightmares!! 10 Aug 2002 http://tinyurl.com/ghgv and http://tinyurl.com/ghgm Depending on the problem with transients, the earth ground may need be enhanced. Important is the neighborhood history. Also important is the geology. Does the ground tend to attract more CG lightning? For example, mid-west storms may be spectacular, but most of the lightning remains sky to sky. WV is a region with high numbers of CG (cloud to ground) strikes per thunderstorm. Those discussions also mention equipotential which is why Ufer grounds and halo grounds make the protector even more effective. Also is earth conductive or is it sand. I believe that previous discussion also tells a story of a house struck multiple times - and lightning rods did not work. Why? Lightning rods were earthed poorly in non-conductive sand. Bottom line - a surge protector is only as effective as its earth ground. In most locations, a single ground rod may provide massive increase in protection. A house that does not at least meet post 1990 National Electrical Code earthing requirements does not have the necessary earth ground. Also in that misc.rural discussion would be how wire must be routed. For example, no sharp bends and no splices. A ground wire bundled with other wires may only induce more surges on that other wire (which is but another reason why plug-in protectors have no effective earth ground). There is much to read. Come back with questions. The simple earthing of surges is surprisingly not intuitively obvious. In discussing this, I was amazed how many don't even know what a Ben Franklin air terminal (lightning rod) does - AND yet would recommend surge protectors. Many even argue pointed verse blunt lighting rods - when earth ground defines the effectiveness of that rod. A surge protector is only as effective as its earth ground. snip Ron |
#27
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In article ,
wrote: My house was built this year, so its earthing should be up to 1990 national building codes. But how can I be sure the builder did it correctly? I don't think this is anything that the local building inspector can test. I doubt he could tell the difference between a 10-inch grounding rod and one that was driven 20 feet into the ground, if he even inspects this feature at all. How can I tell if my house is earthed correctly? Try searching on "National Electrical Code", grounding, lightning as search terms. I found an article he http://bg.ecmweb.com/ar/electric_com...tning_florida/ "He measured the ground resistance of the system using a fall-of-potential meter, gathering a reading of 105 ohms. Though it was high, it wasn't unusual in that part of Florida, despite the area's high water table." "The NEC allows for a maximum resistance of 25 ohms at the grounding electrode (250.56)." Just what I found in a five minute search. As that article notes, ground depends on local geology, so practice could be different between regions of the country. (More rods, different depth, etc.) When I searched on "fall-of-potential meter", it turned out someone made the term up, as there were few hits on that exact phrase. This article describes the method used: http://ceenews.com/mag/electric_quick_primer_grounding/ "The most reliable post-installation testing procedure involves the Fall-of-Potential (three point) method. Utilizing a digital ground resistance meter, two auxiliary electrodes are driven into the soil at predetermined distances as per testing specifications in a straight line from the ground rod under test. The meter supplies a constant current between the ground rod under test and the most remote electrode." Sounds pretty hokey to me. That article at least contains terms that you could use to query a contractor. Paul |
#28
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A ten foot rod with a less than ten foot connection to each
utility provides a major protection improvement. To get additional but lesser improvements, the grounding system gets exponentially larger and expensive. High reliability systems can spend $thousands just to get a minor increase in earthing. The ten foot rod is often more than sufficient. However earth geology itself can be a major determining factor. For example, clay can be an excellent earthing material. Sand can be horrendous. And as the 'house with lightning rods' failure story demonstrated, if something else in the house makes a connection to more conductive (deeper) geology, then the single point earthing can be compromised. To understand earthing, understand your geology. If the house has a water well, this can make a complication that is firstmost solved by routing the water and power lines in at the same single point service entrance. Will the surge use your single point ground or will it cross the house to get to water well? Later could result in household appliance damage AND a damaged well pump. Other factors may make surges problematic such as being at the end of a street and therefore at the end of an AC electric distribution line. Is that a vein of copper, graphite, or iron nearby? Those too could compromise an earthing system that is on the wrong side of the house - farthest from that most conductive earth. As noted, if we built new homes as if the transistor existed, then rebar to reinforce footings are connected to become the earthing system. An Ufer ground that surrounds the building both makes a most superior ground AND makes earth beneath that building equipotential. We would do this to every building if we really were serious about surge protection. Costs so little. Does so much. To improve their earthing system, some bury a bare copper ground wire around the building. This halo ground both makes earthing more conductive AND again makes earth beneath the building equipotential: http://www.cinergy.com/surge/ttip08.htm Another example of everything that could be done in a cell phone tower site is the figure on page 14 of: http://www.leminstruments.com/pdf/LEGP.pdf or the section entitled "Measuring Ground Resistance at Cellular Sites,Microwave and Radio Towers" in: http://leminstruments.com/grounding_...ml/index.shtml Lem Instruments makes equipment to measure earthing - for those who are serious. You need not get so extreme because you don't need the reliability of a power company or a telephone switching station. Above are ideas. Implement any of these ideas if easy. Outside of anomalies such as a vein of buried iron or unusual number of strikes in your neighborhood, then a single 10 foot ground rod (or rods) is often more than enough earthing to eliminate problems from most direct strikes. Should you feel more is needed, then expand a single point ground with more 10 foot ground rods. NEC notes how far apart those rods must be. Best to interconnect those rods with buried ground wires - again per code requirement for wire size and depth. Interconnecting wire supplements - makes that network of ground rods even better. Better to make those below surface rod connections inside a 4 or 6" plastic pipe with a cover so that the below ground rod connection can be uncovered and inspected. All this is the secondary protection system. You should also inspect your primary protection system: http://www.tvtower.com/fpl.html Yes there is much you can do. But again, what is the neighborhood history? Don't remember if those previous posts included application notes from erico.com. Their figure and application note 002 makes another point. Surges are carried into the building even on buried cables. Even buried cables must make a connection to single point earth ground before entering the building. One thing I have seen is some electricians cut the ground rod in half. Too short. That rod must be at least 8 feet down (because the first couple of feet really is not good earthing) AND must remain firm in ground. If you can shake a ground rod, then it is not electrically connected to earth. Yes it is an art - as to what is good enough. Complicating is that earthing measurements are only in resistance. Surges are really more concern with impedance - due to higher frequencies. So yes, a lower resistance can mean a better impedance - most of the time. The art. But as I said, most have more than sufficient earthing with one earth ground rod in good conductive soil and a very short connection to every incoming utility. Inspectors don't verify any of this. Inspector are concerned with human safety. You also want transistor safety. Both use many of the same components. But both have slightly different needs - as that discussion in misc.rural should demonstrate. Milleron wrote: My house was built this year, so its earthing should be up to 1990 national building codes. But how can I be sure the builder did it correctly? I don't think this is anything that the local building inspector can test. I doubt he could tell the difference between a 10-inch grounding rod and one that was driven 20 feet into the ground, if he even inspects this feature at all. How can I tell if my house is earthed correctly? |
#29
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On Fri, 14 Jan 2005 14:23:43 -0500, w_tom wrote:
What you describe as describe as "all SPSes include at least as much separate surge protection on the mains supply line as a decent standalone surge protector would provide;" is really near zero protection for numerous reasons. Both the plug-in UPS and power strip protector have the same protector circuit. And both are typically so grossly undersized to be ineffective. Always start with the numbers. In this case joules. Unless you live in an area with frequent major thunderstorms, your surge protector will mainly be blocking the much smaller surges and spikes on the power line caused by local appliances starting and stopping. If you have a lighting strike near enough to damage unprotected equipment in your house, you may anyway want to replace your surge protectors (or surge-protector containing SPSes), for some of the reasons you imply - you can do that quite frequently for the cost of one good enough not to need replacing! In another post and in those previously cited posts are examples of how joules define protection. Notice that so many plug-in protectors AND their plug-in UPS counterparts may be rated at 345 joules. As joules increase, the life expectancy of that protector increases exponentially. IOW if the plug-in protector is good for two same size surges, then the 1000 joule 'whole house' protector is good for something on the order of 300 of those same size surges. See above. Then it continues farther. The plug-in protector has no earth ground. Therefore the manufacturer avoids the entire topic altogether. This is how one identified ineffective (and grossly overpriced - yes grossly overpriced) plug-in protectors. 1) No dedicated wire connection to earth ground AND 2) manufacturer avoids all discussion about earthing. I live in England - all power circuits installed in the last 40 or 50 years here are wired with a separate earth ground, and all half-way decent UK surge protectors will shunt common-mode surges to this ground. I must admit that I had forgotten that this (wired grounds to every power point) "aint necessarily so" in the rest of the world. Further details will be provided in response to Milleron. But the plug-in protectors are on the order of 10 and 50 times more expensive per protected appliance. So yes, what you are calling cheap protectors are really overpriced and expensive protectors that also are not effective. BTW, UPSes switch in milliseconds. (One must be careful to buy power supplies with numerical specs that read: Hold up time, full load: 16ms. typical). Surges do their damage and are done in microseconds. 300 consecutive surges could pass through a UPS before the UPS even considered switching to battery power. Plug-in UPSes have one function - data protection. They do not provide the hardware protection so often implied. I think that it was perfectly clear from my earlier response that I did not believe that _the_ _SPS_ _component_ of a cheap "UPS" provided any surge or spike protection. You want a UPS that also provides hardware protection? That is typically the building wide UPS that also makes this all so important 'less than 10 foot' connection to earth ground. Plug-in UPSes are for data protection; not for hardware protection. I stand by my original statement, though with the proviso that plug-in surge protectors, to be reasonably effective, must have a separate wired ground connection (which can be, and in the UK usually will be, a connection to a properly wired ground circuit in the house wiring), and must shunt common mode spikes to it. If your system/application/business is so critical that you want a guarantee of 24/7 operation through any reasonably conceivable electrical storm, then the sort of approach to power protection that you advocate makes perfect sense, but most people are not in that position. As I think you or someone else says elsewhere, hardware can be replaced at finite (and often quite low) cost - lost data may be irreplaceable, and can't always be backed up to the minute. Relatively cheap UPSes provide a very high level of data protection gainst brownouts and power outages and (by virtue of their separate surge protection circuitry) a significant, though incomplete, level of hardware protection from the effects of "normally" dirty power. I would be very concerned if someone read your posts and concluded that, if (s)he can't afford to spend $1,000+ on whole-house power protection, (s)he should not bother with anything less. "Peter R. Fletcher" wrote: On Sun, 09 Jan 2005 19:50:06 -0500, (Paul) wrote: ...... wiring exposure to just the power lines. A real ($1K purchase price) UPS would reduce the risk of an AC power event from getting you, and would help protect the PSU from getting damaged. Cheap UPSes offer no protection at all, as they are actually SPS (standby power supplies) - they are a "straight wire" to power spikes, and the unit only cuts over to batteries if the AC power dies for enough milliseconds. I think that you are being unduly negative about cheap "UPSes". You are absolutely correct that they are not true UPSes, since: a) they normally connect the mains power (effectively) straight through to the controlled devices, thus offering no _intrinsic_ protection from spikes; and b) they have to switch to inverter mode when the power fails, which takes finite time. However: a) almost all SPSes include at least as much separate surge protection on the mains supply line as a decent standalone surge protector would provide; and b) All except the cheapest, no-name, ones switch fast enough so that a normal computer system power supply does not "notice" the transient power loss (though network switches, hubs, and the like may "glitch"). For most home and SOHO users, an SPS will provide cost-effective protection against most of the data loss problems which might otherwise be caused by brownouts and/or power outages, while their built in (but unrelated) surge protection circuitry is a _lot_ better than nothing as insurance against damage from power line spikes. Please respond to the Newsgroup, so that others may benefit from the exchange. Peter R. Fletcher Please respond to the Newsgroup, so that others may benefit from the exchange. Peter R. Fletcher |
#30
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On Fri, 14 Jan 2005 23:54:14 -0500, w_tom wrote:
snip Other factors may make surges problematic such as being at the end of a street and therefore at the end of an AC electric distribution line. Is that a vein of copper, graphite, or iron nearby? Those too could compromise an earthing system that is on the wrong side of the house - farthest from that most conductive earth. Interesting point about being the last house on the street. Several years ago, we had a nasty summer electrical storm in central Ohio that knocked out power to many homes and neighborhoods. We had no lightning real close to my house, but we lost power. We have underground wiring with transformers every so often. I'm sure it's exactly like overhead wires. At any rate the crew that came out pointed out that our transformer was the LAST one in a long chain. They thought the strike was distant and surged all the way to that point. It ruined our transformer (took 30 hours to replace it), but there was no damage at all in any of the houses that drew power from that particular transformer. What happened in this scenario? If the surge went to earth at that point, what killed the transformer without hurting any of the transformers farther up the line? snip Ron |
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