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[Weaver]

This morning I was watching the approaching lightning storm at blitzortung.org getting closer. There were various strikes in Ireland, in South Wales and then up here in the Small Isles there was a strike in the sea just north of Eilean Chanaidh which is just a few miles to the west of Skye. I should have pulled the modems at that point but, stupidly, I didn’t and before I knew it there was a strike right on the Heasta road a few hundred metres north of the house.

Janet pulled all the modems and the Firebrick went into failover mode, switching to internet access over 3G using its 3G USB ‘dongle’ NIC. This promptly racked up a bill of £13.68 for AA/AQL/Three 3G SIM network charges. AA said that 0.682Gb had been transferred and I’m presuming that that means bits, not bytes, because of the lower case “b” even though such ”bits“ usage seems really unusual. I make that 85.25 MB (bytes). This huge amount was lessened by the fact that I later connected my iPad to Janet’s iPhone, which has an EE SIM and which was sharing out its EE 4G network connection over 802.11 (a sharing-over-802.11 facility which Apple calls ‘hotspot’). Janet’s EE account has a lot of unused ‘data’ allowance which I too could take advantage of on my iPad by using Janet’s ‘hotspot’ service.

When I later dared to plug the modems back in, it then looked as if all four lines (apparently) were down. A bit of diagnosis, then trying a new known good modem in line 1, and things still didn’t work, and it turned out the lightning had completely destroyed the 8-port ZyXEL VLAN/MUX switch. The copper DSL lines themselves though seem to have all survived without damage.

Janet then plugged in the spare/backup VLAN MUX switch that we had just had delivered a week or so ago from Andrews and Arnold, and ta-DA! Two DSL lines came back up.

Talk about timely, so lucky that for no particular reason I had decided to be prepared and recognise that the only piece of hardware for which I did not have on-site swap-out kit was the small VLAN/MUX switch. I even have a second firebrick, an FB2500, but I realised a few weeks ago that the small switch was the weak link, because I had no spares. And the spare was delivered just in time for the killer lightning strike.
 
The next job this afternoon was to configure two new spare modems from the reserve stock to go into those slots. I spent what felt like an hour faffing around checking the contents of config files because I hadn’t left them annotated properly. I was in pain and over-tired and was sitting in a chair in the office helping Janet with all the plugging and unplugging. I just ended up too tired, couldn’t think straight and in too much pain so I actually couldn’t configure the modems. I realised I would have to do a pin-in-hole Johnson/Burakkucat reset first, in order to gain control because the new modems I had obtained from eBay were not talking to me, so a full reset was required before I could even start configuring them. I was just too tired so decided to abandon the work of modem-configuring until the next day.

So in the end I plugged two good, already-configured DLink DSL-320B-Z1 modems into slots #3 and #4 and then all four lines were good for the night.

Tomorrow I will have to attack a load of modems, at least two, poking them and configuring them; not just two, I should do the backlog of modems I have bought but have never configured.

The small switch was not showing per-port LEDs above the ethernet sockets but the "Power" LED was lit, so it seems certain that that MUX switch is indeed really stuffed. Could anyone tell me how a switch decides to light one of these port LEDs, what criterion it uses?

The replacement small switch shows lit LEDs above the ethernet ports that have something plugged into them, I don’t know if that means something at the near end, far end or if both ends have to be ‘good’ in some sense.

• Lesson to be learned - lightning can appear to ‘jump’ >20 miles with no warning. You see a strike on the lightning maps that is some distance away and you think ‘oh the danger zone is over there’ which is completely false; the thundercloud could already be right over the top of you, and when you’re looking at the lightning strike maps, nothing is going to tell you where the undischarged dangerous clouds ( ie those about to discharge ) are at the present moment. I have never seen a situation like this before.
• Minimum radius. I will have to be much much more paranoid in future. If there is a strike anywhere on the lightning map within say 70 miles radius then it’s time to unplug the modems.
• I really need to have modems ready configured, standing by, and that means ready to go, not needing configuration first. When I get new modems for use in reserve stock, I should be resetting them and configuring them straight away. It also means that newly arriving modems then get inspected and can get tested to some very basic level.
• And I also need to document everything, there’s now a program that I’ve written for the iPad that writes slot-n adapted versions of a master template modem config XML config file, but it isn’t at all obvious to the reader how to declare/define a new / updated master template config that is used by the slot-n  copy/adaptation program. Firstly I could not just see where the master config is set, where it’s definition lives and secondly I couldn’t see which file is the basis of this because there was no documentation. Grrrr. :-(

[johnson]

So what path do you think led to the switches demise? It blew up two modems as well as the switch, so the surge passed through the ethernet transformers of both modem and switch?

Do you have DECT phones blow up as well?

Have you thought have some sort of remote controlled relay on the phone lines to either allow you to manually isolate everything, or even automate it with your lightning detector?

What mechanisms do the exchanges employ to not fry gear every time there is a storm?

Sorry for all the questions, just curious as all electrical storms have done to my connection is cause errors and retrains.

[burakkucat]

 

[Weaver]

So what path do you think led to the switches demise?

I don’t know I’m afraid. Anyone have any suggestions? It was inky a few hundred metres away and right in the phone line from the lightning strike map.

It blew up two modems as well as the switch, so the surge passed through the ethernet transformers of both modem and switch?

Correct.

Do you have DECT phones blow up as well?

Don’t have any any more. For some reason couldn’t work out how to mate them to the the Siemens VOIP box and was too tired to slog through a long session with AA support; AA support that kit because they supplied it to us.

Have you thought have some sort of remote controlled relay on the phone lines to either allow you to manually isolate everything, or even automate it with your lightning detector?

An interesting idea. I’m not any good at electronic hardware, and too ill to have the concentration nor can I sit upright. I’m afraid the disconnect thing wouldn’t work because you don’t get any warning at all on some occasions, Sunday being the perfect example. Sometimes there’s a strike right on you and no others nearby beforehand. Thus afternoon there were three strikes on in Broadford itself and two in the sea in Broadford bay, and zero warning. Pulled out the modems too late today but luckily no damage done.

What mechanisms do the exchanges employ to not fry gear every time there is a storm?

Our experienced engineers will be able to answer that. I’m presuming gas discharge tubes.

Sorry for all the questions, just curious as all electrical storms have done to my connection is cause errors and retrains.

Our problem is the extremely long line 7300m which leaves us very vulnerable and exceptionally vulnerable to GPR/EPR, plus there’s the exceptionally wild weather at certain times of the year.

[Weaver]

More strikes all the time this afternoon (Monday). Modems unplugged but too late.

Today I have just bought 8 more modems from an eBay seller. Bought 4 last month. I’ve found a supplier who delivers pristine boxed ZyXEL VMG1312 B10A units that look certainly as if they’re brand new never used. They still have the plastic film round the unit, plus a cd and leaflet, and all the usual stuff you get in a box when something is brand new.

I’ve also ordered yet another MUX switch from AA.

The only defence I could think of is either an RF or optical bridge x 4 between each of the modems and the MUX, or between MUX and firebrick. Janet would go mad if I wanted her to put in 4 x 2 opto-isolators or ethernet fibre media converters. And the modems would still be unprotected.

I could claim on my insurance for the equipment damage, but there’s a substantial excess and they’d perhaps put our premiums up. Ultimately insurance is the only practical solution as I don’t have access to gas discharge tubes.

I’m too tired to do modem-poking today. I’ve found the instructions Johnson supplied on how to reset modems that are unresponsive - very much appreciated. I wonder if there’s a way of making it a bit easier and quicker to do the whole thing of resetting each modem and then configuring it with alien 192.168.1.199 etc IP settings on my iPad?


Looking at freemaptools and measuring distance, I see that the lightning ‘jumped’ from just north of Eilean Chanaidh to Heasta here a distance of 24 miles.

[PhilipD]

More strikes all the time this afternoon (Monday). Modems unplugged but too late.

Today I have just bought 8 more modems from an eBay seller. Bought 4 last month. I’ve found a supplier who delivers pristine boxed ZyXEL VMG1312 B10A units that look certainly as if they’re brand new never used. They still have the plastic film round the unit, plus a cd and leaflet, and all the usual stuff you get in a box when something is brand new.

I’ve also ordered yet another MUX switch from AA.

The only defence I could think of is either an RF or optical bridge x 4 between each of the modems and the MUX, or between MUX and firebrick. Janet would go mad if I wanted her to put in 4 x 2 opto-isolators or ethernet fibre media converters. And the modems would still be unprotected.

I could claim on my insurance for the equipment damage, but there’s a substantial excess and they’d perhaps put our premiums up. Ultimately insurance is the only practical solution as I don’t have access to gas discharge tubes.

I’m too tired to do modem-poking today. I’ve found the instructions Johnson supplied on how to reset modems that are unresponsive - very much appreciated. I wonder if there’s a way of making it a bit easier and quicker to do the whole thing of resetting each modem and then configuring it with alien 192.168.1.199 etc IP settings on my iPad?


Looking at freemaptools and measuring distance, I see that the lightning ‘jumped’ from just north of Eilean Chanaidh to Heasta here a distance of 24 miles.

Thought you had no problems :-)  Have you not tried some surge protection, you can get them for telephone lines, there should be something in the master socket (gas discharge) but I expect those are fried already.

[PhilipD]

Hi Weaver

What about something like this https://mikrotik.com/product/sxt_lte6_kit, it has the modem and external antenna inside so you get the maximum signal straight to the modem.  Less concerns regarding lightening as no connection to your phone line, you can simplify your kit completely and should end up with much faster speeds.  I suspect it will cost you considerably less overall as you could do away with 3 phone lines.

Regards

Phil

[Weaver]

I’ve tried cheap DSL surge protectors but they wrecked the signal. Thanks very much for that Mikrotik url - will investigate. Could combine that with L2TP to AA, although dealing with the UTP issues would be a challenge though.

Sorry, by ‘problems’ I meant transient dsl copper line problems aside from lightning damage. Mea culpa. My problem yesterday was my poor health, stamina. Anyone who gets a lightning strike will have to do some maintenance afterwards.

[burakkucat]

. . . there should be something in the master socket (gas discharge) but I expect those are fried already.

Unfortunately not.    They were removed from the NTE5 specification a number of years ago. 

[PhilipD]

Unfortunately not.    They were removed from the NTE5 specification a number of years ago. 

Didn't know that.  Maybe they were proving ineffective then?

Regards

Phil

[sevenlayermuddle]

Didn't know that.  Maybe they were proving ineffective then?

Regards

Phil

My understanding is...  that they only shunted across the pair, making them completely pointless when confronted with effects of lighting, which is likely to be appear as common mode spikes.  They also presented a small capacitance across the line which might, in theory at least, have detrimental effect on DSL.

Similar three pole devices exist which might help a great deal with lightning but the centre pole must be earthed if they are to do any good.  I think there was a time, early half of last century, when an earthed lightning protection device was included on post office lines.  I would imagine that modern equivalents of such devices will play a part in protection of exchanges, but the problem at consumer end would be absence of an earth conductor.

Useful discussion here...

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

[Weaver]

I agree with 7LM. There’s just nowhere for all that 30kA to go; it’s useless without getting it into earth, surely?

[burakkucat]

Maybe they were proving ineffective then?

And were also shown to be detrimental to an xDSL service.

[sevenlayermuddle]

And were also shown to be detrimental to an xDSL service.

I’m curious, have you seen any reference source that quantifies the detriment?

If done ‘properly’ with a 3 pole GDT device and earth, which is effectively two devices in series, the effective shunt capacitance would be halved, and so the detriment halved.  But I’m not sure if capacitance is all there is to consider.

[burakkucat]

I’m curious, have you seen any reference source that quantifies the detriment?

Unfortunately not.

If done ‘properly’ with a 3 pole GDT device and earth, which is effectively two devices in series, the effective shunt capacitance would be halved, and so the detriment halved.  But I’m not sure if capacitance is all there is to consider.

Yes, but as we know, the devices were two pole and thus just clamped the pair together.

The initial "modern day" (i.e. post 1980) plug & socket system, before the genesis of the NTE5, was with the various line-jacks and those constructed as a "master" socket were fitted with a metal oxide varistor (MOV) for over-voltage protection. With age, they had a tendency to shunt the pair with non-linear frequency dependent effects.