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Author Topic: Lightning Storm Damage (Jan 2020) - Modems 2 and 3 Down  (Read 2885 times)

Alex Atkin UK

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Re: Lightning Storm Damage (Jan 2020) - Modems 2 and 3 Down
« Reply #30 on: January 18, 2020, 01:38:03 AM »

Indeed, I'd imagine the reason it so thoroughly fried the IO chip on the motherboard was because it will have jumped to ground within the chip.

Although if the voltage is high enough, it would have found somewhere to do so regardless.

What amazed me though was while it did all that damage, the phone line was completely unaffected.  I'm using the same drop wire today.

The most scary part was how it also caused all the phones in the house to ring continuously, like in a horror movie.  Apart from the cloud of smoke next to the fuse box. ???
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kitz

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Re: Lightning Storm Damage (Jan 2020) - Modems 2 and 3 Down
« Reply #31 on: January 19, 2020, 10:32:40 AM »

From all the info available BT/Openreach does not get involved in lightning protection.
There's an interesting article here which seems to imply that as far as they are concerned protection costs more than replacement of equipment.
https://www.britishtelephones.com/lightng.htm

I can't find anything about their own buildings, but I should image they would have some form of lightning rod/ lightning conductor plus surge protection and backup.   I seem to recall a few years ago on social media a video of a storm hitting an exchange somewhere up here in the Lancs/W Yorks which someone had filmed from their bedroom window..  iirc the lights inside the building dimmed briefly.  I can't find it again now as it was going back several years but if memory serves correct it supposedly hit their (backup) power generator and there was black smoke briefly rising above it :(

It would appear that when it comes to business and workplaces there are regulations in place for Lightning Protection and Compliance and if necessary there are firms such as Voltix which will carry out risk assessment, and any required installation and maintenance of lightning protections systems. There are also specialist firms who design and implement solutions against lightning strikes and power surges for data and telecom businesses.  Obviously though this is over-kill for Weaver.

Back to Openreach telco equipment in the home/office...  I found this article whereby a lightning strike to a substation at a Business Park took out telephony equipment to most of the businesses in the area....  and at the bottom there is a single paragraph about one of the business who suffered little damage due to having their telephone lines protected by these Telecom Line Protection devices.

In fact on this page there is other equipment which may be of interest?
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benji09

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Re: Lightning Storm Damage (Jan 2020) - Modems 2 and 3 Down
« Reply #32 on: January 19, 2020, 10:56:05 AM »

  I did have a further thought about Weaver's earth. Perhaps a 3 metre copper pipe buried in his grass, flat in the ground as deep as it could be put in. I assume the top soil is more than a few inches deep in the garden. I would think that where  Weaver lives, there should be plenty of rain to keep it wet. If this is carried out, the connection to the earth wire should thick, and also soldered above ground and painted over, insulated from the weather. Putting the pipe in the ground can be carried out by making a V groove in the soil with a fork and a spade. After the work is finished the soil can pushed back with a foot!  Maybe Weaver could get some help with this?
 
« Last Edit: January 19, 2020, 10:48:34 PM by benji09 »
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Weaver

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Re: Lightning Storm Damage (Jan 2020) - Modems 2 and 3 Down
« Reply #33 on: January 20, 2020, 07:14:31 AM »

What’s the best way to connect the earth up to the ‘impact’ sites, the sites from which current needs to be effectively carried away?

If Mrs Weaver can recruit some help for a bit of digging, then we do have some wet soil. Neither she nor I are up to any digging anyway.

I don’t know if electricians would do that kind of work ?
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sevenlayermuddle

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Re: Lightning Storm Damage (Jan 2020) - Modems 2 and 3 Down
« Reply #34 on: January 20, 2020, 08:59:40 AM »

What’s the best way to connect the earth up to the ‘impact’ sites, the sites from which current needs to be effectively carried away?

Personally I’d say you need to resolve that issue first, before thinking about earth rods.  Ie...  To what things in/around the home will this earth rod be connected, and how will currents flow from problem points (such as phone wires) towards the earth rod?   I  remain unconvinced that enhanced earthing will do any good, unless you have a design to address these specific stray currents.

An Electrician would be able to help with earthing of your mains electricity but the purpose of that earthing is to ensure that fuses and other protective devices ‘blow’ when certain dangerous electrical faults develop.    That’s different from lightning protection.

Then again, if you’d actually be connecting this rod to anything then you’d be modifying the house electrical earthing, and I’d certainly say you need to consult a well qualified Electrician to ensure your plans comply with current wiring regulations.
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aesmith

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Re: Lightning Storm Damage (Jan 2020) - Modems 2 and 3 Down
« Reply #35 on: January 20, 2020, 09:26:10 AM »

Incidentally if the house earthing system is really PME then the earth potential within the house may be different to the true earth potential away from the house, due to neutral current on the combined neutral/earth conductor.
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benji09

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Re: Lightning Storm Damage (Jan 2020) - Modems 2 and 3 Down
« Reply #36 on: January 20, 2020, 09:23:33 PM »


  Fine advice about the electrician.  My house was built in 1934, and uses the original wiring from the street. The earth is taken from the protection screen of the the street cable. Our water pipes in the road, if original, are lead ( hard water area! ), therefore well earthed outside the house anyway. Some of the houses in the road have had their mains supply reinstalled as `PME' supply, which is now the norm for new work. My own internal wiring is PME as is a requirement anyway, although my feed has not changed.
  Reference Weaver broadband lines, anything he connects to his phone line is likely to wreck is broadband, and I think BT try to avoid fitting surge protectors for this reason. But, maybe, Weaver's problem could be also due to what get induced onto his mains supply feed, with an earth which is all over the place, making mains surge protectors ineffective. Bear in mind if the BT lines are are referenced to earth at the exchange, and the earth potential at his home is not stable,, then that could cause a problem.   
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sevenlayermuddle

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Re: Lightning Storm Damage (Jan 2020) - Modems 2 and 3 Down
« Reply #37 on: January 20, 2020, 10:32:28 PM »

The earth is taken from the protection screen of the the street cable.

That sounds like TNS, rather than PME.

Quote
My own internal wiring is PME as is a requirement anyway, although my feed has not changed.

Not sure what you mean?

Quote
Reference Weaver broadband lines, anything he connects to his phone line is likely to wreck is broadband

I had also heard of that effect.   But looking at the specifications of a 3 pole GDT device, with max capacitance of 5pF, I’m open minded that it’s just a rumour.   

It is the simple fact it is 3 pole device with an earth, even a crappy earth, that makes it hold promise, rather than having no earth at all.    Here’s the link (again) to the spec of 3 pole GDT supposedly in BT’s parts box...

https://assets.mayflex.com/downloads/EXCEL/E0206-S-Exc-21A.pdf

And here’s the link to the place that mentioned it, posted by Kitz as well as myself...

https://www.britishtelephones.com/lightng.htm

Ref ‘surge protection’ I think we need to differentiate between those that create a short circuit to protect against high voltages across the phone line, and those that shunt to earth a common mode voltage at the phone lines.   The former are pointless when it comes to lightning and the latter require an earth, which (expense) is arguably why BT do not fit them at the subscriber end.

I would still love to know whether BT fit 3 pole GDT (or similar) at the exchange end. Note that protection of “telephone exchanges” is listed as one of the applications of 21A  in above link. :)
« Last Edit: January 20, 2020, 10:43:25 PM by sevenlayermuddle »
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Weaver

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Re: Lightning Storm Damage (Jan 2020) - Modems 2 and 3 Down
« Reply #38 on: January 21, 2020, 01:41:56 AM »

I have a friend who is a qualified electrician and runs his own firm. All I need to do is persuade him to come up for a holiday.
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neil

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Re: Lightning Storm Damage (Jan 2020) - Modems 2 and 3 Down
« Reply #39 on: January 21, 2020, 05:48:58 AM »

it looks scary but here we dont have any lighting protection installed here in our homes
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aesmith

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Re: Lightning Storm Damage (Jan 2020) - Modems 2 and 3 Down
« Reply #40 on: January 21, 2020, 11:48:12 AM »

Not sure what you mean?
I was wondering that myself, as far as I'm aware the difference between TNS and TNCS (whether or not PME) is only external, whether there are separate N and E conductors in the supply.  N and E should be separate on the consumer side in any case.   Unless he means his internal bonding is all to the standards required for PME.
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benji09

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Re: Lightning Storm Damage (Jan 2020) - Modems 2 and 3 Down
« Reply #41 on: January 21, 2020, 05:56:04 PM »


 Yes all my internal pipes are bonded to the earth at the meter. Think this is now a requirement whatever your mains feed is. Reference the suppression components on a BT line, I think all types present some form of capacitance across the line. I agree that any simple suppression applied between the pair would be useless. Hence the need for an earth at his site. But that earth should also include the mains earth, since his modems are connected to the mains supply. It is no good if the main earth is floating all over the place, if the BT side of it is not. Perhaps a change to Weavers mains supply to the type normally seen on camp sites where a RCCB is used and a local earth is supplied may be an option. I don't know the official term for it TNK?????. I am not an electrician by trade  obviously !
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sevenlayermuddle

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Re: Lightning Storm Damage (Jan 2020) - Modems 2 and 3 Down
« Reply #42 on: January 21, 2020, 07:12:22 PM »

I am not an electrician by trade  obviously !

With respect, I think some of us had guessed as much. :)

Personally I have a BSc in Electrical and Electronic  Engineering, though that was many decades ago.   Even so, whilst I enjoy tinkering with electronics devices for my own use, and I enjoy speculating on challenges such as how best to protect modems from stray lightning pulses, I would be very unlikely to ever suggest changes to mains supply or earth bonding.   That is a topic fraught with danger and way more specialised than a typical Electronics degree course, even if  ‘electrician’ may sound like a lesser qualification.

I did have some modifications done to my own detached garage a few years ago, converting the exported PME to TT, but I kept my opinions to myself down and allowed the professional electricians to tell me what should be done, and then allowed them to carry out their work.   The other advantage of that approach is they have indemnity insurance, should you need to sue them.  ;D
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benji09

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Re: Lightning Storm Damage (Jan 2020) - Modems 2 and 3 Down
« Reply #43 on: January 21, 2020, 08:59:57 PM »

   I was required by the gas company, before I even had central heating installed in my home, to carry out the required earthing. It seems that it is not unknown for the supply company to lose the earth when they make repairs in the road. Also, as I said all new work done to mains supplies is to the `PME' (TN...) standard, so carrying out PME work at the customer's home covers all future safety needs. After I had carried out the earthing work, I was forced to have normal central heating installed due to the hot air system I previously had, could not be maintained any longer.   
« Last Edit: January 22, 2020, 04:09:14 PM by benji09 »
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Weaver

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Re: Lightning Storm Damage (Jan 2020) - Modems 2 and 3 Down
« Reply #44 on: January 21, 2020, 10:57:53 PM »

I have consigned two modems to the bin. The other two appear fine but I can’t tell. Should I bin them anyway just to be in the safe side? Where safe means reduced performance?

I think not, as the stats look normal. The modems and the MUX switch they were connected to were not earthed. The chain is : four modems, VLAN MUX/DEMUX switch and then the Firebrick router then my main switch, the firebrick is earthed as is the main switch, so I suppose the firebrick would be the exit point if current heading to earth? The firebrick looks fine and the small MUX switch is behaving as normal. I’m getting an additional spare MUX switch. I would think that the very short ethernet CAT6 cable going from modem to MUX which is shown in the earlier image blackened would be reasonably high resistance as it’s such small diameter copper although it is short. The high(-ish) resistance if indeed that’s fair would limit the current - you’re not going to fit 30kA down that wire - although as this was not afaik a lighting strike in the cable, as, according to the map, the nearest strike was about 500-1000m - away I can’t tell exactly - so I assume this was induced current.

I’m surprised that we didn’t get the modems unplugged in time. The modems were unplugged from the wall, just not quite soon enough. I have four additional modems in order, and I have two spares currently I think. It just goes to show that lightning is really unpredictable - when there is any in the area, you could be next - it doesn’t "move", with a predictable behaviour pattern, aside the general wind direction. The areas where there has been no strike are going to be the next source candidates, because they haven’t yet been discharged, so that is why it hops around.
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