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 Post subject: Lightning strikes!
PostPosted: Tue Oct 08, 2013 5:12 pm 
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Location: Michigan, USA
We had a very loud lightning strike last Friday night. Woke up to discover a couple of cable boxes not working, our TV had one HDMI connection fried, the modem was out of order, and a DVD player was also toast. All the toasted items were connected to surge protectors.

Right next to the modem sits a UPS to which my desktop and router were plugged in. As near as I can tell, they are both fine.

Thank goodness for the UPS. Should I plug the modem into it as well, even though it has a backup battery inside? I've read where that is a bad idea.


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 Post subject: Re: Lightning strikes!
PostPosted: Tue Oct 08, 2013 8:16 pm 
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My UPS has coax connectors for the cable modem to plug into/out of for surge protection and the AC for the cable modem is most definately connected to my UPS (as well as the router).

Your surge protector mfgr should pay for the fired parts.

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 Post subject: Re: Lightning strikes!
PostPosted: Tue Oct 08, 2013 11:48 pm 
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Stephen wrote:
All the toasted items were connected to surge protectors.

You might read the manufacturer's specifications. Those power strips do not claim to protect from a typically destructive surge. Numbers alone are damning. Somehow that power strip must stop or absorb a surge ... that is destructive at hundreds of thousands of joules. How many joules does that protector claim to absorb? Hundreds? A thousand? IOW it only claims near zero protection.

Are all bathroom GFCIs, smoke detectors, furnace, dishwasher, clocks, refrigerator, and dimmer switches damaged? What protected them? Same thing that also protected a desktop and router. Best protection at any appliance is already inside the appliance. If a UPS was doing effective protection, then those other unprotected appliances (ie smoke detectors, clocks, refrigerator) must be damaged. Read spec number for that UPS. It claims even less protection than power strip protectors. Why assume the UPS did anything when even the manufacturer does not claim that protection?

Another and completely different device does protection of everything. Now is an ideal time to learn why a surge was permitted inside to hunt for earth destructive via appliances. Unfortunately, it is also called a surge protector even though it is and works completely different. Connects hundreds of thousands of joules where no damage results. And costs many times less money - about $1 per protected appliance.

You had near zero protection as even by spec numbers state. Now is a best time to learn about what actually does protection - earth ground - and what is required to connect destructive surges to that protection - one 'whole house' protector.


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 Post subject: Re: Lightning strikes!
PostPosted: Wed Oct 09, 2013 3:21 am 
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Location: UK
Surge protectors, UPS, power conditioners and everything else like that are only of limited use if the electrics of the building are not sound and if the electrical supply is good, you shouldn't need any of them. Unless you really do have power cuts every week you shouldn't need a UPS.

Is your house itself correctly earthed? In the event of a lightning strike it should be able to dissipate the strike - this isn't just about protecting your electricals but also stopping your house burning down! The next thing is that your electrics should not make use of structural parts of the house (ie. copper piping) for the earth. The plumbing should be earthed but should not be used as the earth for electrical connections. The ideal is that structural earthing and electrical earthing should be kept separate right until the point where they go into the ground (ie. before the consumer unit), that way it keeps the separate and keeps your electrical earth clean.

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 Post subject: Re: Lightning strikes!
PostPosted: Wed Oct 09, 2013 3:59 am 
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Surge protectors are only able to deal with small electrical fluctuation on the power lines. Lightning often comes into the ground, or through the signal. A friend had a small computer network, and the the only thing not on UPS battery backup was a laser printer connected to the LAN, which was off at the time of the lightning strike. All the network cards were taken out because the surge came in through the ground.

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 Post subject: Re: Lightning strikes!
PostPosted: Wed Oct 09, 2013 4:42 am 
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NeilBlanchard wrote:
All the network cards were taken out because the surge came in through the ground.

OK. Remember this is electricity. To have damage, both an incoming path and outgoing path must exist. If an incoming path was ground, then what was an outgoing path? Destructive surges seek earth ground. If incoming from ground, and no outgoing path, then damage is not possible.

Facilities that cannot have damage always connect a surge to earth either via a wire or via a 'whole house' protector. Nothing (ie UPS) stops, blocks, or absorbs a surge. Routine protection even implemented over 100 years ago means a surge always connects to earth so that a surge current is not inside the building.

A surge current seeks earth ground. A building only wired to meet all 2013 safety codes (only one incoming AC wire is earthed) does not avert a destructive hunt for earth. One typiically destructive path is incoming on AC mains (ie hot / black wire). Outgoing via network cards to the modem. And then to earth via earthed protection that already exists (required by codes) on telephone and cable wires. Now that computer has both an incoming and outgoing path. What is often damaged? The outgoing path - ie network cards.

Computer had an incoming (AC electric) path and an outgoing (NIC) path to earth. Both paths are necessary to have that damage. Damage is when some (at least one) AC electric wires did not connect to earth at the service entrance.

A protector is effective only if properly earthed. UPS, for example, has no dedicated and low impedance (ie 'less than 10 foot') earth ground connection. And does not even claim that protection. If a 'whole house' protector is not earthed at the service entrance, then a surge can be inside hunting for earth ground destructively via appliances.

Appliances are not protected by grounding the appliance. That would only make an appliance a better and destructive connection to earth. Protection means earthing a surge BEFORE it can enter the building. One 'whole house' protector with an always required low impedance (ie no sharp wire bends; no splices) connection to earth. Then a surge (ie a direct lightning strike far down the street) does not go hunting for earth destructively via household appliances.

Safety codes do not require all AC electric wires to be earthed. Those wires only connect destructive surges to earth IF a 'whole house' protector makes that low impedance connection to single point earth ground. All four words in that last expression are also significant. In each above case, a surge was all but invited to go hunting for earth destructively via appliances. With or without a UPS.

Routine for 100 years was direct lightning strikes without damage. Careful attention focused on what absorbs that energy (single point earth ground) and what makes a low impedance connection to earth (ie wire or a 'whole house' protector). A solution that typically costs about $1 per protected appliance.


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 Post subject: Re: Lightning strikes!
PostPosted: Wed Oct 09, 2013 4:17 pm 
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Yeah, the lightning has just jumped across a mile (or so) of open sky, it can probably come through the circuit traces and out again. There is a lot of potential between different parts of the ground.

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 Post subject: Re: Lightning strikes!
PostPosted: Thu Oct 10, 2013 12:50 am 
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westom wrote:
A surge current seeks earth ground. A building only wired to meet all 2013 safety codes (only one incoming AC wire is earthed) does not avert a destructive hunt for earth. One typiically destructive path is incoming on AC mains (ie hot / black wire). Outgoing via network cards to the modem. And then to earth via earthed protection that already exists (required by codes) on telephone and cable wires. Now that computer has both an incoming and outgoing path. What is often damaged? The outgoing path - ie network cards.

I agree that that can be a cause for damage and that is only going to be a problem when the computer is not adequately earthed itself. The earth resistance down a network connection is going to be pretty big whereas for a properly earthed mains outlet you can expect around 1 Ohm. With a 1 Ohm earth connection, the chance of surge damage through a network adaptor with a resistance of maybe 100 Ohms is minimal.

westom wrote:
A protector is effective only if properly earthed. UPS, for example, has no dedicated and low impedance (ie 'less than 10 foot') earth ground connection. And does not even claim that protection. If a 'whole house' protector is not earthed at the service entrance, then a surge can be inside hunting for earth ground destructively via appliances.

Surge protectors on consumer units are a good idea I agree. We have one since we had PV panels installed. Here in the UK it is mandatory for all new consumer unit installations and replacements but that still leaves 90% of houses with old units that don't have a surge protector. The way you do things in the US does scare me a little I have to say so I'm not surprised (but still disappointed) that you don't have it mandated either. Hearing of someone here who has had electrical equipment damaged due to a lightening strike is almost unheared of in this country although I have heard of an instance of a fault at a substation which ended up blowing some peoples appliances up.

westom wrote:
Appliances are not protected by grounding the appliance. That would only make an appliance a better and destructive connection to earth.

I wouldn't totally agree here. If the appliance is correctly earthed then the earth impedance is lower so yes it does make it more likely to conduct but also if the appliance (or something along the way) is fused or on an RCD then it is more likely that the fuse will blow or the RCD trip before damage occurs - the chassis and earthing of an appliance will take many more amps without damage than a network connection.

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 Post subject: Re: Lightning strikes!
PostPosted: Thu Oct 10, 2013 5:52 am 
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edh wrote:
I agree that that can be a cause for damage and that is only going to be a problem when the computer is not adequately earthed itself. ...
Surge protectors on consumer units are a good idea I agree. We have one since we had PV panels installed. Here in the UK it is mandatory for all new consumer unit installations and replacements but that still leaves 90% of houses with old units that don't have a surge protector.

In the UK, surges are so rare that if any protector was effective, then nobody has surge damage. Since appliances contain robust protection, then damage in the UK is rare. But UK has surge damage because most have no effective protection from that rare type of surge that overwhelms existing appliance protection. Protectors adjacent to appliances will somehow stop a surge? Of course not.

Earthing an appliance makes that appliance an easier and destructive path to earth. Apparently a few concepts are not understood. Some call that third prong on a power point an 'earth ground'. It is not. It is only a safety ground. Earth ground is another and different ground.

Inside your computer is a digital ground and analog ground. That is different from the safety ground, which is different from the earth ground, which is different from a floating ground found inside some electronics. Those grounds may be interconnected. And are electrically different.

For example, many only assume a wire from a power point ground to switchboard is 1 ohm. It better not be that high resistance. Meanwhile, resistance is irrelevant. Critically important here is impedance. That wire that should be more like 0.1 ohm resistance can also be 120 ohms impedance during a surge. Assume a surge is tiny - 100 amps. 100 amps times 120 ohms means the voltage (end to end) on that wire is something less than 12,000 volts. Where is the earthing? Does not exist because that wire is too long, has splices, has numerous sharp bends, and is not separated from other non-grounding wires.

The term is 'less than 3 feet'? It was critically important. Numbers in that above paragraph demonstrate one reason why. And demonstrate why a power board or appliance only has a safety ground connection; not an effective earth ground connection.

You also assumed earth ground conductivity that is irrelevant because it is high. A surge current flows through miles of earth (to earthborne charges) no matter what you do. The question is how that current gets to earth. From the cloud, through 3 kilometers of sky, then through kilometers of earth to earthborne charges. Ben Franklin demonstrated how to make that connection without structure damage. A lightning rod does not do protection. (Many foolishly argue pointed verse blunt). It is simply a connecting device to what does the protection - the earth ground electrode.

Lightning striking any utility wire (overhead or underground) far down the street is a surge incoming to all household appliances. Which one makes a destructive connection to earth? That one is damaged. Same 'Ben Franklin' concept applies. A protector does not do protection. It is simply a connecting device to what does the protection - an earth ground electrode.

In both cases, protection of a structure or appliance is not defined by what everyone sees - a lightning rod or protector. In every case, protection is defined by the most important component in every protection 'system': earth ground. Both lightning rod and protector are only as effective as the most important item in any protection system: earth ground.

Telcos all over the world do not attach protectors adjacent to their electronics. That would only make surge damage easier. In every telco (ie BT) exchange, always installed is the single point earth ground (better earthing) and 'whole house' protectors. Every wire that enters that building is earthed by a protector. To make protection more effective, telcos increase separation between protector and electronics by up to 50 meters. Separation (and that 'less than 3 meter' connection to earth) is critical for protection.

How often is a destructive surge? For homes, typically once every seven years. A number that is much larger in the UK. However telcos connect their £multi-million switching computer to all other buildings in town. That means about 100 surges with each storm. How often is your town without phone service for four days while BT replaces that computer? Never. Because they use proven protection. Protectors make a connection from every incoming wire as short as possible (ie 'less than 3 meters') to single point earth ground. Protectors are separated from electronics by up to 50 meters.

Foolish is to think anything (fuse, protector, open switch) will block a surge. It was not stopped by kilometers of a world's best insulator - air. Why would millimeters inside a fuse, RCD, etc stop a surge? It doesn't. Nothing stops a surge. As in nothing. Furthermore a fuse, RCD, etc take milliseconds to trip. A surge is done in microseconds. Maybe 300 consecutive surges could pass through an RCD before it even thought about tripping. Anything that would stop a surge is best called a scam.

Either a surge connects to earth harmlessly outside. Or it connects to earth destructively via appliances (or a structure - even wood is an electrical conductor). Only the consumer makes that choice. Damage means a surge was all but invited to go hunting for earth inside and destructively via appliances. Protection means that current has a much lower impedance (ie 'less than 3 meter') connection to earth on a path that remains outside the building. And so again, protection is defined not by a protector. Protection is defined by the quality of and connections to single point earth ground.

It should be obvious that nothing (not an RCD, switch, fuse, filter) stops or blocks a surge. Do not earth an appliance. That only makes that appliance the best and destructive path to earth. Earth a surge (maybe 20,000 amps) before it enters the building.

You had damage? That was the path an electric current took from cloud to distant earthborne charges. Damage because that current had (simultaneously) both an incoming and an outgoing path to earth. At the same time a surge is incoming to a power board protector, the same current is outgoing into attached appliances. Nothing stops or blocks that current. High voltage (and therefore destructive energy) only exists when something foolishly tries to stop that current.

A protector is only as effective as the quality of and connection to single point earth ground. Earth the surge; not an appliance.


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 Post subject: Re: Lightning strikes!
PostPosted: Thu Oct 10, 2013 7:31 am 
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Problem is: Your DSL-line and your modem isn't grounded, at least in germany. We had some customers with dead modems after a lightning strike. Only a few had more damage done, the surge obviously was passed through the modem or router via network cabling. WiFi users were not impacted ;-)


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 Post subject: Re: Lightning strikes!
PostPosted: Thu Oct 10, 2013 8:43 am 
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westom wrote:
Protectors adjacent to appliances will somehow stop a surge? Of course not.

I'm not going to fully reply to what you have written as I think you misunderstand what I say so much of it is not applicable. I did not suggest surge protection on appliances but on a consumer unit:
http://en.wikipedia.org/wiki/Consumer_unit
So yes, what I was talking about being mandated here is exactly the same as you suggest for a 'whole house surge protector'. I hope this clears that up.

westom wrote:
Inside your computer is a digital ground and analog ground. That is different from the safety ground, which is different from the earth ground, which is different from a floating ground found inside some electronics. Those grounds may be interconnected. And are electrically different.

This I know. Plus if you do interconnect appliances with DC switch mode power supplies (for example a video cable) you can get interference caused by their 0V lines being slightly different. Worse still you could have interconnected medical equipment with applied parts over which that interference is flowing - this I have had and it can be at unsafe levels but what you absolutely mustn't do in such circumstances is earth the patient. Typically a lack of decent earthing on different equipment can be a cause or alternatively it can be down to poor designs of switch mode power supply on one piece of equipment or other. This kind of interference is also indicative of where you might see a surge to earth running - from a poorly earthed thing to a well earthed thing.

westom wrote:
Lightning striking any utility wire (overhead or underground) far down the street is a surge incoming to all household appliances. Which one makes a destructive connection to earth? That one is damaged.

Years ago my Dad watched a lightening strike hit a village, it caused arcing across overhead electrical wires all across the village below. It was a small close knit village and no one reported having anything blown. The substation for the village tripped out so the electricity went off but that's it. This is in the days before surge protection was at all common place and many of the houses were old so probably sub standard electrcially. We don't get lightening damage to houses electrics.

westom wrote:
How often is a destructive surge? For homes, typically once every seven years. A number that is much larger in the UK.

Your cite? My counter cite is that I've lived here for 30 years and it hasn't happened yet to anywhere I've lived or worked nor anywhere any of my friends or relatives have worked either. That would be 1 in >10000 years I would think.

westom wrote:
Do not earth an appliance.

I'm sorry but this advice is highly unsafe. Any appliance with exposed metal parts must be earthed. Any kind of electrical safety test will have this as a requirement. Maybe you value your computer equipment over your own personal safety and that of others? Keep that advice to yourself if that is the case. Is it better for computer equipment itself in general use to not be earthed? I'd say no, partly for the interference issues listed above when interconnecting different systems but also because computer chips are EM sensitive and with a metal case, you improve the level of EM protection by earthing the case.

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 Post subject: Re: Lightning strikes!
PostPosted: Thu Oct 10, 2013 12:27 pm 
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I lived in Florida for a number of years and grew up in the midwest. I've seen lots and lots of lightening strikes. While you'd expect it to follow the obvious least resistance path, sometimes odd shit happens. A friend's house was struck...not the roof, not the aluminum guttering, not the metal utility pipes. Instead, it struck the concrete floor in their roofed patio via the screened (plastic) window. It spalled a nice divot in the floor.

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 Post subject: Re: Lightning strikes!
PostPosted: Fri Oct 11, 2013 4:19 am 
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edh wrote:
westom wrote:
Do not earth an appliance.

I'm sorry but this advice is highly unsafe. Any appliance with exposed metal parts must be earthed. .
I never said an appliance must not be safety grounded. I was very specific about the difference between safety ground and earth ground in that longer post. Did you get the point that wall receptacle safety ground is not earth ground? Do not earth ground an appliance. In many venues, that is a code violation. Safety ground the appliances - a completely different ground. Safety ground is what a third prong on a power point does. Earth ground is completely and electrically different. Earth grounding an appliance makes surge damage to the appliance easier.

What you called a consumer unit was also called the breaker box or switchboard. Protectors in that panel are useful only in the consumer unit that also has a low impedance connection to earth ground. Only one panel typically has that earth ground connection. To be low impedance, that connection must be as short as possible, no sharp bends, not inside metallic conduit, etc. Only then can a protector be part of a 'system' that protects from one type and typically destructive surge.

Same protection for phones / DSL is typically connected to the same earth ground. In North America, this has always been installed for free. If your telco does not install it, then you must install it to have DSL protection. It was also explained in that long post that completely applies to your situation. If any wire enters without a connection to earth, then all protection is compromised. The connection to earth is via a wire (ie cable TV) or via a 'whole house' protector (DSL). Because (and again) protectors do not do protection. Because protectors are only connecting devices (like a wire) to what does protection.

Another long post from an AT&T Forum specifically discusses DSL protection. And describes all other protection - since the same principles apply even to a protector in your consumer unit.

Surges that do damage typically occur once every seven years. A number that varies significantly even in the same town. Other factors (even geology) affect that number. To know the number in your neighborhood would require at least ten years of neighborhood history. All appliances already contain robust protection. Just another reason why surges do not happen hourly or daily. Surge protection is about an event that occurs maybe once every seven years. Because the only surge that concerns you is one so robust as to overwhelm protection inside appliances (ie DSL modem).


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 Post subject: Re: Lightning strikes!
PostPosted: Fri Oct 11, 2013 4:27 am 
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An AT&T forum provided "How can I protect my DSL/dialup equipment from surges?":
Quote:
Surge protection for DSL and dialup service.
Surge protection takes on many forms, but always involves the following components: Grounding bonding and surge protectors. ...
Grounding is required to provide the surge protector with a path to dump the excess energy to earth. A proper ground system is a mandatory requirement of surge protection. Without a proper ground, a surge protector has no way to disburse the excess energy and will fail to protect downstream equipment. Bonding is required to electrically connect together the various grounds of the services entering the premises. Without bonding, a surge may still enter a premise after firing over a surge protector, which will attempt to pass the excess energy to its ground with any additional energy that the services surge protector ground cannot instantly handle, traveling into and through protected equipment, damaging that equipment in the process. ...
Now, if all the various service entrance grounds are bonded together there are no additional paths to ground through the premise. Even if all of the grounds cannot instantly absorb the energy, the lack of additional paths to ground through the premise prevents the excess energy from seeking out any additional grounds through that premise and the electronic equipment within. As such, the excess energy remains in the ground system until dissipated, sparing the protected equipment from damage. ...
By far, the whole house hardwired surge protectors provide the best protection. When a whole house primary surge protector is installed at the service entrance, it will provide a solid first line of defense against surges which enter from the power company's service entrance feed. These types of protectors can absorb/pass considerably more energy than any other type of protector, and if one does catastrophically fail, it will not typically be in a living space. ...
Plug in strip protectors are, at best, a compromise. At worst, they may cause more damage than they prevent. While they may do an acceptable job of handling hot to neutral surges, they do a poor job of handling any surge that must be passed to ground. ...
Then, to add insult to injury, some strip protectors add Telco and/or LAN surge protection within the same device, trying to be an all-in-one sale. Remember bonding? When Telco or LAN protection is added to a strip protector, if the premise ground, which is not designed to handle surges, cannot handle all of the energy, guess where that excess energy seeks out the additional grounds? You got it! The Telco and LAN connections now becomes the path, with disastrous results to those devices. ...
As noted previously, protection means knowing where hundreds of thousands of joules harmlessly dissipate. Otherwise protection from direct lightning strikes and smaller (but potentially destructive) surges is ineffective. Protection is always about the single point earth ground.


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 Post subject: Re: Lightning strikes!
PostPosted: Fri Oct 11, 2013 10:21 am 
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westom wrote:
Did you get the point that wall receptacle safety ground is not earth ground?

I know it the US it isn't but we do use earth ground for mains outlets here.
Quote:
Q. Is grounding via domestic mains the same as using an external grounding rod?
A. Yes. In fact a modern domestic electrical system has just such a grounding rod buried in the ground (usually just outside the house). This grounding rod is connected via the domestic wiring system to the earth pin on every mains socket.

http://www.groundology.co.uk/faqs

westom wrote:
Protectors in that panel are useful only in the consumer unit that also has a low impedance connection to earth ground. Only one panel typically has that earth ground connection. To be low impedance, that connection must be as short as possible, no sharp bends, not inside metallic conduit, etc. Only then can a protector be part of a 'system' that protects from one type and typically destructive surge.

Yes, like the 10mm earth cable that comes out of our consumer unit, goes through the wall and straight into the ground outside, as mandated by our electrical standards. The same earth that is connected to all of our sockets too and is earth ground.

westom wrote:
Surges that do damage typically occur once every seven years. A number that varies significantly even in the same town. Other factors (even geology) affect that number. To know the number in your neighborhood would require at least ten years of neighborhood history.

It's never happened anywhere I've lived or any of my friends or family has lived. My grandfather has lived in one house for 40 years and never had any surge damage to anything. So as I said, we don't typically get damage to electrical equipment from lightning strikes. Even with the mandatory earth grounding of electrical outlets that you do not advise.

Of course one way to avoid damage on outgoing communications would be optoisolation. You can get optoisolators for CAT5 networking that just couple two cables passively but for telephone this would require some sort of active amplification on both sides.

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 Post subject: Re: Lightning strikes!
PostPosted: Fri Oct 11, 2013 3:54 pm 
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edh wrote:
I know it the US it isn't but we do use earth ground for mains outlets here.

US receptacles also have three prongs; the third is a safety ground. A popular UK myth is that US power points (receptacles) only have two prongs.

Your earth ground does same as earth grounds all over the world. 'Context' applies. Your citation discusses 50 hz electricity and safety ground. It says nothing relevant to this topic. Does not provide numbers. Does not even discuss the relevant concept: impedance. Context: that citation only discusses 'human safety'. This topic is about a completely different electrical anomaly and 'transistor safety'.

That citation also discusses a receptacle tester - that only tests safety ground. Disconnect an earth ground wire at the earthing electrode (obvious do not actually do this). That tester still says safety ground is OK. Because that tester obviously cannot report on the other ground - earth ground. As noted earlier, many grounds, all interconnected, are electrically different. Ground relevant to the topic is earth ground - which is not a receptacle's safety ground.

OP's damage was to a TV, DVD player, cable box, and modem. All connected to surge protectors that define - read spec numbers - protection superior to what a UPS does. How can that be? Why were appliances damaged when connected to a more robust surge protector? Especially when appliances without any protector (GFCIs, dishwasher, door bell, furnace, clocks, dimmer switches, refrigerator, washing machine) were not damaged? A damning fact. If a UPS is so effective, then other appliances (without a protector and no UPS) should be damaged. What protected those unprotected appliances?

The answer is found in concepts defined by over 100 years of well proven science. That surge was incoming to every household appliance. Which ones were damaged? Those that also made a best outgoing path to earth. Damage can only exist when both an incoming and an outgoing path exists (electricity as even taught in primary school science). TV, DVD player, cable box, and modem connected that surge to earth. Those four damaged appliances protected all other appliances.

A surge current, all but invited inside, went hunting destructively for earth. Why did that surge need not find earth destructively via a furnace, refrigerator, dimmer switches, clocks, night light, or GFCIs? Why should it? Superior internal protection and another connection to earth via damaged appliances means appliances without UPS or surge protector were protected. Having found a better path to earth via TV, DVD, etc, then a surge need not overwhelm protection already inside a recharging mobile phone, CFL bulbs, microwave, and smoke detectors.

Adjacent protector did exactly what the manufacturer said it would do. UPS manufacturer specifications say its protection is even less. Read manufacturer spec numbers. Even the AT&T forum, discussing protection all over the world, makes this obvious. Protection of most everything was provided by better protection already inside appliances. A surge voltage did not overwhelm existing protection because the TV, cable box, DVD, and modem destructively connected energy harmlessly to earth.

In Michigan, superior solutions to avert future damage are provided by companies known by guys for their integrity. Including Leviton, Square D, Ditek, General Electric, Intermatic, Syscom, ABB, Siemens, and Polyphaser - to name but a few. A Cutler-Hammer solution once sold in Lowes and Home Depot for less than $50. What makes this 'whole house' solution superior - especially during lightning? Honest and useful answers use perspective and numbers. Superior protectors have a dedicated wire for the "low impedance" (ie 'less than 10 foot') connection to "single point earth ground". Not wall receptacle safety ground. Earth ground.

More numbers. Since a typical lightning strike is 20,000 amps, then a minimal 'whole house' protector is 50,000 amps. Effective protectors do not fail. Nobody need know a surge existed. No appliance damage. A properly sized (ie 50,000 amps) 'whole house' protector also is unharmed.

OP can learn from the damage. His surge protectors did what the manufacturer said it would do. So he had damage. Joules numbers say a UPS is even lesser protection. Effective protection is a 'system'. A wire or protector do same; are only a connecting device to what does protection - 'single point earth ground'. Where hundreds of thousands of joules are absorbed harmlessly outside the building.


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 Post subject: Re: Lightning strikes!
PostPosted: Sat Oct 12, 2013 1:25 am 
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Location: UK
westom wrote:
US receptacles also have three prongs; the third is a safety ground. A popular UK myth is that US power points (receptacles) only have two prongs.

I know you have 3 prongs. I never said you didn't. :roll: Please bear in mind I have done electrical troubleshooting in over 20 countries and know the different socket types! How you connect that 3rd prong up IS different, hence why some buildings in the US have used aluminium in the past for cabling, or make use of the copper plumbing or steel structure for the earthing path itself.

westom wrote:
Superior protectors have a dedicated wire for the "low impedance" (ie 'less than 10 foot') connection to "single point earth ground". Not wall receptacle safety ground. Earth ground.

Yes, like the 10mm earth cable that comes right out of our consumer unit with it's built in surge portector and goes into the ground outside via a large earth rod. The same earth connection which is also connected to all electrical outlets in the house because we do use earth ground and don't do crazy things like splicing together cables, using the plumbing as the earth or using the structure of the building as the earth.

I'm getting pretty tired of this discussion. I only came into this to point out that poor earthing of the structure can be a problem in the event of a lightening strike to the building as appliances blowing is minor compared to your house burning down. Continuously you dismiss what I say assuming that I have misunderstood you and that I don't know the difference between different earth types. I don't want to get into an argument about one or other standard of electric installations is better but all I can clarify is that we do mandate surge protection at the consumer unit, it is properly earthed with an earthing rod, as is everything else.

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 Post subject: Re: Lightning strikes!
PostPosted: Sat Oct 12, 2013 5:06 pm 
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edh wrote:
Yes, like the 10mm earth cable that comes right out of our consumer unit with it's built in surge portector and goes into the ground outside via a large earth rod. The same earth connection which is also connected to all electrical outlets in the house because we do use earth ground and don't do crazy things like splicing together cables, using the plumbing as the earth or using the structure of the building as the earth.
Those 'crazy connections' were mistakes of the past - 40 and 60 years ago. A water pipe earth ground is now insufficient for human safety. And typically worse for surge protection. Times and standards have long since changed. (Unfortunately grandfathering may create problems.)

Described was a 'whole house' protector inside the consumer unit. What makes it so effective? Not just any earth ground. Single point earth ground. And a wire from that protector to earth that is every meter short as possible (ie 'less than 3 meters'). That protector is only as effective as its earth ground. Because a protector does not do protection. Earth ground does the protection. You apparently understand that. But repeated to be quite clear to others (not just the OP) what is important.

A wire that connects a consumer unit to wall receptacles is not and was not earth ground for many electrical reasons - even 60 years ago. Those reasons are even more critical when doing surge protection. Apparently you appreciate that a 4 mm dia (apparently you are using a 10 mm cable) connection to a dedicated earthing electrode. Wire thickness is mostly irrelevant. Length of that wire is critical. Not for human safety. Critical for transistor safety.

A protector attached to a breaker box, switchboard, or consumer unit can make that all so important, low impedance connection to earth. So that energy is not inside the building. Energy (current) not inside a building hunting for destructive paths to earth. Protection has always been about connecting the current harmlessly outside to earth. Always.

OP has symptoms of a classic lightning strike far down to the street to utility wires. Classic of a surge entering on AC electric. Then hunting for earth destructively via appliances. A best connection to earth is often destructively via appliances connected to cable, satellite dish, or telephone lines. Since those routinely have (low impedance) earthed protection. If incoming on AC mains, then energy was permitted inside to hunt destructively for earth. Incoming to a cable box via its power cord. Outgoing to earth on its cable connection. Meanwhile, an adjacent protector did what its manufacturer said it would do.

A 'whole house' protector is simple science. With a number that defines protector life expectancy: 50,000 amps. Earth ground is the art. Defines protection during each surge. Same art says why wall receptacles do not provide earth ground. And why an earth ground wire from the 'whole house' protector must have no sharp bends, no splices, not inside metallic conduit, must be separated from other non-grounding wires, and of course as short as possible (ie 'less than 10 feet'). Not a thicker wire. Shorter.

If the consumer unit protector has a low impedance connection to earth, then it protects all appliances (assuming that nation's telco and cable company have installed protection required in Michigan).


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 Post subject: Re: Lightning strikes!
PostPosted: Sun Oct 13, 2013 1:10 am 
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westom wrote:
Wire thickness is mostly irrelevant. Length of that wire is critical. Not for human safety. Critical for transistor safety.

Length of the wire is important but I would also say that cross section is important and have first hand experience of this. If the earth wire is not the same diameter or larger than the live or neutral cores then you can put yourself in a difficult situation where the earth is unable to to take the same current rating as the supply. I would never accept an earth smaller than live or neutral for new installation.

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 Post subject: Re: Lightning strikes!
PostPosted: Sun Oct 13, 2013 5:42 am 
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edh wrote:
Length of the wire is important but I would also say that cross section is important and have first hand experience of this.

That demonstrates confusion of human safety requirements with transistor safety. Human safety requirements (ie code) defines wire thick enough (ie 4 mm) for human safety. That same wire is more than thick enough for transistor safety.

Code for human safety says nothing about wire length. Electricians know human safety requirements. But often do not understand electrical concepts necessary for transistor safety (ie wire length, no sharp bends, etc).

Any homeowner can inspect his own earth ground. If that bare, copper, quarter inch (4 mm) ground wire goes up over the foundation and down to an earthing electrode, then protection (for transistor safety) is compromised. A 'whole house' protector is not properly earthed. That wire is too long, has many sharp bends going over the foundation, and is probably bundled with other wires. Protection compromised.

Better surge protection means that ground wire goes through a foundation and down to earthing electrodes.

This is but another example of why earthing to meet code (for human safety) may be insufficient for transistor safety. Another example of the 'art' of surge protection.

An AC utility demonstrates another critically important example of the 'art'. Single point earth ground. Demonstrated are good, bad, and ugly (preferred, wrong, and right) earth grounds:
http://www.duke-energy.com/indiana-busi ... tip-08.asp
This 'wrong' example means surges may go hunting for earth destructively via household appliances. An example of the 'art' that applies to grounds in all nations.

OP had damage because his protectors and UPS had no earth ground. Anything above that compromises earth ground exists mutliple times in a safety ground wire from that power point (receptacle) to breaker box (switchboard, consumer unit). Protectors adjacent to appliances have no earth ground. Therefore cannot protect from from typically destructive surges. His damage is classic of appliances overwhelmed by a surge that was all but invited to go hunting for earth destructively inside.

'Art' of protection is about what does protection during each surge - a low impedance connection to single point earth ground.


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