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Author Topic: Line 3 fail  (Read 1592 times)

Weaver

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Re: Line 3 fail
« Reply #15 on: October 22, 2019, 09:28:47 PM »

You’re right, I think your analysis of what’s going on in the cable is spot on, makes a lot of sense. The result of huge induced current must be a frightful mess. So it could be gel crimps that are burned out ?

The other thing I thought about is the D.C. resistance of the cable per metre is probably a lot less than the resistance of each joint, perhaps because the contact surface area is smaller and there’s a metal-metal contact, so it could be that a joint is a current bottleneck. So joule heating which is I2R therefore being proportional to R will be higher at the joint bottleneck. Does that sound right?

I wonder what state all the main insulation is in if the whole copper gets cooked?


Makes me think: what has possibly happened to my NTE5s? Wonder if they got cooked too, so that there might have been a deleterious effect on them. The performance looks excellent now so I have nothing to complain about and no obvious reason why I need to replace master sockets. But it makes me wonder.

NB Janet says the technical term for an inhabitant of Heasta is a ‘Heastag’ /hestak/ pronounced ‘haystack’, plural Heastagan (haystackən). I object to this on the grounds of the fact that the feminine diminutive -ag means that it only can apply to the female inhabitants such as herself. She has clearly been listening to too much Gaelic.
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burakkucat

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Re: Line 3 fail
« Reply #16 on: October 22, 2019, 10:56:23 PM »

So it could be gel crimps that are burned out ?

I think that could well be possible, yes.

Quote
The other thing I thought about is the D.C. resistance of the cable per metre is probably a lot less than the resistance of each joint, perhaps because the contact surface area is smaller and there’s a metal-metal contact, so it could be that a joint is a current bottleneck. So joule heating which is I2R therefore being proportional to R will be higher at the joint bottleneck. Does that sound right?

Hmm . . . I'm balancing on top of the fence. Having passed through the era of the dreaded "blue-bean" crimps, which were just brass with serrated teeth to puncture the insulation, the idea was to ensure similar metal to similar metal contact with a pressure induced cold-weld (by plastic deformation of the metal at the point of maximum pressure). However with a many-thousand-volt transient surge, I'm not so sure if the normal Ohmic behaviour would be followed.

Quote
I wonder what state all the main insulation is in if the whole copper gets cooked?

A very nasty, smelly, blackened mess. And possibly stuck to the duct - if ducted.

Quote
Makes me think: what has possibly happened to my NTE5s? Wonder if they got cooked too, so that there might have been a deleterious effect on them. The performance looks excellent now so I have nothing to complain about and no obvious reason why I need to replace master sockets. But it makes me wonder.

The many thousands of metres, and section joints, between the proposed point of electrical interaction at Harapul and your NTE5s, in the office, at northern Heasta was probably enough to save those devices. That Mrs Weaver had disconnected the four patch leads, before the "main event" occurred, undoubtedly saved the analogue front-ends of the four VMG1312-B10As.
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Weaver

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Re: Line 3 fail
« Reply #17 on: October 23, 2019, 01:57:13 AM »

So is the insulation possibly wrecked for good now in the entire cable length then, in the whole entire length to Heasta? Maybe the current flow along different lengths of the cable wasn’t equal, somehow, but that would mean current getting out ‘sideways’ somehow as we can’t violate the continuity equation and conservation of charge; there isn’t enough capacitance to store that amount of charge temporarily so instantaneous current into any one section surely has to equal current out and there’s no getting out of that.

I wonder if the engineers do temporary repairs which are enough to get the customer going again and then report to management that cables are stuffed, recommending replacement?

I see your point about non-linear behaviour at the joints when under extreme conditions or if a bad joint, non-ohmic indeed.

Is the current carrying capacity of gel-crimp contacts quite large? Or are the only meant for use with very very small currents?
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Weaver

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Re: Line 3 fail
« Reply #18 on: October 23, 2019, 02:58:19 AM »

BTOR has now repaired the line again. Came out today.

Quote
Yesterday 15:46:40      Note Today 15:09:33 Track PSTN Fault 5-7-187270071594 Notes Field: 22/10/2019 15:08:00 - ===Point Of Intervention notes=== Between this point... - Location: Jb23 jcn dp26. Garden no.3 - Work Point: JB23 And this point... Plant details... - Plant affected: JNT50 - Plant type: MC31 Multiple Intervention?: Y ===Point Of Intervention notes ends=== (No manually entered closure notes) === QBC Summary Start ===Customer Report: End customer advised of no dial tone / voice on the line.\n\n Actions to resolve: Engineer has resolved the fault located at the D-side including aerial cables / lead-in / block terminal.The fault was located outside the end customer's curtilage and shown by soot / blackened wire / cable.The fault was fixed by clearing in joint.\n\n Additional information: Engineer has visited end customer premises.\n\n Final test results: Final PQT performed at the NTE back plate.The test passed with amber parameters on 2019-10-22T14:57:41.\n\n Final alternate test results: Final FastTest performed from the customer premise.The test passed on 22/10/2019 15:04:39.=== QBC Summary End ===   stuart@a
Yesterday 15:46:37      Sent KCI email weaver@Weaver.com 2019-10-22 15:46:31 Line down (LostCarrier)   KCI
Yesterday 15:46:37      Sent KCI sms Janet 2019-10-22 15:46:31 Line down (LostCarrier)   KCI
Yesterday 15:46:37      Sent KCI tweet Weaver 2019-10-22 15:46:31 Line down (LostCarrier)   KCI
Yesterday 15:45:54   Yesterday 15:46:18   Test SNR reset: RateBandDS=160-24384 InterleaveLevelDS=On TargetMarginDS=3dB RateBandUS=32-Uncapped InterleaveLevelUS=On TargetMarginUS=9dB:SNR Recalculation initiated which will enable the line to reach optimum speed, stabilization retrains can be expected over the next couple of days.   david@a
Yesterday 15:45:26   Yesterday 15:45:34   BT Test xDSL Status Check:Pass Standalone sub test passed successfully.Pass OK. Circuit In Sync BRAS=253kb/s FTR=2278kb/s MSR=2848kb/s ServOpt=1 I/L=I
A SERVICE OPTION CHANGE ORDER IS IN PROGRESS ON THIS LINE
Up Sync=376kb/s LoopLoss=40.6dB SNR=6.4dB ErrSec=0 HECErr=0 Cells=0
Down Sync=288kb/s FTB LoopLoss=65.5dB SNR=24dB HIGH ErrSec=0 HECErr=N/A Cells=0   david@a
Yesterday 15:09:37      Track PSTN Fault 5-7-187270071594 Informational Message: 4150 Response Required - Fault Report Cleared   bt
Yesterday 15:09:37      Track PSTN Fault 5-7-187270071594 Estimated Response Time: 2019-10-22T23:59:59   bt
Yesterday 15:09:37      Track PSTN Fault 5-7-187270071594 Clear: 82.2 In Joint AreaCable (Underground)   bt
Yesterday 15:09:37      Track PSTN Fault 5-7-187270071594 Status: Open - Clear Unconfirmed   bt
Yesterday 15:09:33      Track PSTN Fault 5-7-187270071594 Notes Field: 22/10/2019 15:08:00

===Ring ahead information===

Primary EU contact name : Weaver
Primary Contact no : weaver
What was the outcome of the call ? : Successful call
Call date & time : 22/10/2019 09:37

===Ring ahead information ends===

===Point Of Intervention notes===

Between this point...
- Location: Jb23 jcn dp26. Garden no.3
- Work Point: JB23
And this point...

Plant details...
- Plant affected: JNT50
- Plant type: MC31

Multiple Intervention?: Y
===Point Of Intervention notes ends===

(No manually entered closure notes)

=== QBC Summary Start ===Customer Report: End customer advised of no dial tone / voice on the line.\n\n Actions to resolve: Engineer has resolved the fault located at the D-side including aerial cables / lead-in / block terminal.The fault was located outside the end customer's curtilage and shown by soot / blackened wire / cable.The fault was fixed by clearing in joint.\n\n Additional information: Engineer has visited end customer premises.\n\n Final test results: Final PQT performed at the NTE back plate.The test passed with amber parameters on 2019-10-22T14:57:41.\n\n Final alternate test results: Final FastTest performed from the customer premise.The test passed on 22/10/2019 15:04:39.=== QBC Summary End ===   bt
Yesterday 15:09:33      Track PSTN Fault 5-7-187270071594 Informational Message: 4465 Please refer to the Notes field for the actual message   bt
Yesterday 15:09:33      Track PSTN Fault 5-7-187270071594 Estimated Response Time: 2019-10-22T23:59:59   bt
Yesterday 15:09:33      Track PSTN Fault 5-7-187270071594 Clear: 82.2 In Joint AreaCable (Underground)   bt
Yesterday 15:09:33      Track PSTN Fault 5-7-187270071594 Status: Open - Implementing Solution


I found a page concerning the JB23.

Amber parameters - is that the same term as used in connection with DLM as used in Kitz’s discussion thereof? Or maybe I could be ‘green’ but am not achieving that, because of extreme line length?

Funny about that rather high 65.5dB attn - that’s not good compared with the usual figure, but the current reality is 64.5dB which is normal, so nothing to worry about. Wonder why it changed - maybe because of an unusual bits-per-bins allocation at the time ?
« Last Edit: October 23, 2019, 03:39:46 AM by Weaver »
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Chrysalis

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Re: Line 3 fail
« Reply #19 on: October 23, 2019, 05:29:29 AM »

Ask AA about the amber, I guess they will be open about it and tell you, curious as well. :)
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burakkucat

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Re: Line 3 fail
« Reply #20 on: October 23, 2019, 04:59:32 PM »

So is the insulation possibly wrecked for good now in the entire cable length then, in the whole entire length to Heasta?

It would really depend upon the conditions at the time of the "event". Earlier you mentioned that Mrs Weaver's information network had observed a flock of Openreach vans at the Broadford exchange. I suspect that the over-voltage protection devices (near-instantaneous A-wire, B-wire and low-impedance earth connection clamped together) would have required replacing.

Quote
I wonder if the engineers do temporary repairs which are enough to get the customer going again and then report to management that cables are stuffed, recommending replacement?

Again, I suspect that would depend upon circumstance.

Quote
Is the current carrying capacity of gel-crimp contacts quite large? Or are the only meant for use with very very small currents?

I've never seen the design specification for gel-crimps but I believe they should be good for up to 500V DC with currents in the mA range.
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burakkucat

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Re: Line 3 fail
« Reply #21 on: October 23, 2019, 05:14:56 PM »

Just had a thought . . .

Suppose the entire length of one 100-pair cable (or two 50-pair cables) section needs to be replaced from a joint chamber on the A87 all the way to Heasta. What would minimise the financial outlay? To replace like with like? Or to install an N-fibre optical cable?  :-\
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Weaver

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Re: Line 3 fail
« Reply #22 on: October 23, 2019, 10:01:32 PM »

So if the whole thing needed to be replaced, might that mean an FTTC cab in Heasta too? As there are lots of cabs in Harapul, Breacais and Broadford itself.
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burakkucat

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Re: Line 3 fail
« Reply #23 on: October 23, 2019, 10:18:28 PM »

So if the whole thing needed to be replaced, might that mean an FTTC cab in Heasta too?

Who knows? But if the metallic pathway is seriously degraded right down to the shoreline then perhaps native FTTP would be more cost effective.
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Weaver

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Re: Line 3 fail
« Reply #24 on: October 23, 2019, 11:23:07 PM »

@chrys  - I did ask AA about ‘amber’ - will perhaps hear tomorrow as it was way too late.
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Weaver

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Re: Line 3 fail
« Reply #25 on: October 24, 2019, 01:30:29 PM »

AA said "Amber is impacted service, essentially long lines etc."
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