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Topic Title: Opps !
Topic Summary: UKPN had a small problem
Created On: 26 April 2013 06:32 PM
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 26 April 2013 06:32 PM
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slittle

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 26 April 2013 06:38 PM
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OMS

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LoL - do you trust your distributor to get your supply to you safely !! - how hard can it be.

OMS

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Failure is always an option
 26 April 2013 07:29 PM
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slittle

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The guy standing next to the hole was priceless.... If you saw a big hole with burn marks around it would you stand beside it ???

Stu
 26 April 2013 09:40 PM
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UKPN

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this is what happens when you dont do your equipotential bonding!

Regards.
 26 April 2013 09:56 PM
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dbullard

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Originally posted by: UKPN

this is what happens when you dont do your equipotential bonding!



Regards.


Main or Supplementary .............................. just out of interest, I live in a street with a PME supply that every 6 months we have a "joint " go bang pop fizz, so is that also down to "Bonding " issues or just crap cable in the ground that should really now be "overlaid " due to having more joints than cable, funny thing is I can tell the guy where the joints are before they get the "magic map" out f the van.

Regards

A humble consumer and lowly electrician

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www.quest-electrical-sw.co.uk
 26 April 2013 09:59 PM
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leckie

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This supply had a plastic incoming pipe that hadn't been bonded properly. it was only in 2.5.
 26 April 2013 10:03 PM
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slittle

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I'm guessing it was HV so us lowly mortals didn't need to worry about the bonding.

The report said three bangs and I seem to remember that parts of the HV network tends to auto reclose three times before locking out. I'll stand corrected on that by our DNO colleagues


Stu
 26 April 2013 10:11 PM
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SKElectrical

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Originally posted by: slittle
The report said three bangs and I seem to remember that parts of the HV network tends to auto reclose three times before locking out. I'll stand corrected on that by our DNO colleagues



I believe it depends on the machine they are using, and how many fuses are loaded into it. It varies.
 26 April 2013 10:27 PM
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Legh

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Originally posted by: leckie

This supply had a plastic incoming pipe that hadn't been bonded properly. it was only in 2.5.


What do you mean by not properly bonding plastic pipes in 2.5

Legh

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 27 April 2013 11:17 AM
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peteTLM

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Originally posted by: SKElectrical

Originally posted by: slittle

The report said three bangs and I seem to remember that parts of the HV network tends to auto reclose three times before locking out. I'll stand corrected on that by our DNO colleagues







I believe it depends on the machine they are using, and how many fuses are loaded into it. It varies.


LOL. A machine fed with sacrificial fuses. Would'nt be technology along the lines of an ACB then?

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Lack of planning on your part doesn't make it an emergency on mine....

Every man has to know his limitations- Dirty Harry
 27 April 2013 11:18 AM
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505diff

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Looks like an inspection cover is already blown open so would it be an LV link box or has a LV fault blown the cable and damaged a near by HV cable, as the report said about 1800 customers were effected, I doubt you would have that many on a 630a fuse, but then it's London and most of those cables are over a 100 years old so anything goes. Does the word 'safety' now have the same meaning as 'profit' as that's UKPN top prority!
 27 April 2013 11:21 AM
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peteTLM

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Looks like a BT cover IMHO

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Lack of planning on your part doesn't make it an emergency on mine....

Every man has to know his limitations- Dirty Harry
 27 April 2013 12:12 PM
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alancapon

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This is likely to be an HV fault, as the arc didn't last as long as I would expect for LV. I would imagine that the fault was reclosed either by an "auto-restore" scheme designed to minimise outage times or directly from the Control Room. Depending on the amount of information available about the location of the fault, this can lead to the faulty cable section being re-energised as part of the fault location process. It is rare for a cable fault to breach the pavement surface, but it looks like the original fault breached the surface, giving a channel for the second arc to exit above ground.

It is likely that the cable damage was caused by others excavating in the vicinity of the cable, damaging the outer sheath. This damage could have been days, weeks or months ago. The issue really lies with the contractor doing the damage not informing the DNO of the possible damage, perhaps trying to avoid the repair bill.

Regards,

Alan.
 27 April 2013 12:50 PM
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slittle

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On the BBC London news last night there were some new pictures of the cables in the trench.

Almost certainly HV PILC and it would appear there were old joints either involved in or next to the burnt bits.. It did look like LV cables next to them so.........

Stu
 28 April 2013 10:34 AM
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OMS

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Originally posted by: UKPN

this is what happens when you dont do your equipotential bonding!

Regards.


LoL - care to explain that in simple terms in relation to the faulted HV cables - just face it, your network is old and knackered and has suffered from decades of under investment. Isn't that why you are now playing about with 25kV systems to squeeze as much out of the infrastructure as possible without spending any real money.

What you guys need is a good consultant to give you objective, strategic advice on how to run a network.

Regards

OMS

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Failure is always an option
 28 April 2013 10:54 AM
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slittle

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What they've got is some great stakeholders who give them objective advice on how they think they should run their network...... Trouble is unlike consultants they do it for free !

It's an ageing network that needs investment but as Alan has pointed out the cable was probably hit by mick and paddy who just covered it back up. My guys had a duct last week where it had clearly been smashed by a LP firm whilst installing tape and rods and then "repaired" with two plastic buckets.

Stu
 28 April 2013 11:00 AM
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ebee

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"repaired" with two plastic buckets.

That`s advance then on an old tobacco tin (unearthed) LOL

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Regards,
Ebee (M I S P N)

Knotted cables cause Lumpy Lektrik
 28 April 2013 11:39 PM
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alancapon

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My favourites so far have been a damaged LV pot-end (a joint put on the end of a cable run to insulate and seal the cores) repaired with a bin-liner and tape after being hit with a "big yellow digging machine" and an 11kV cable hit with a jack hammer that was repaired using pvc insulating tape.

The LV pot-end went bang before the builder responible had finished on site. The HV cable had been back-filled and the road surface reconstructed on top of it before going bang several weeks later.

Regards,

Alan.
 29 April 2013 05:41 AM
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ebee

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I know a chappie, head of a plumbing outfit, who installed a 2.5 T & E with no protection, 150mm below his drive and it lasted about 20 years until it went bang.

He blamed one of his workers who had used a lump hammer about 2 metres away 3 days before the bang.

LOL

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Regards,
Ebee (M I S P N)

Knotted cables cause Lumpy Lektrik
 29 April 2013 02:00 PM
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Zuiko

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HV circuits have auto-reclose facilities when they have overhead sections (due to nuisance tripping from branches, animals etc.)

I'd be suprised if this network was a HV auto-reclose: it is just too dangerous (as we have seen from the video)

The reclose is normally from a breaker in the primary, but often you will get section breakers along the circuit.


SKElectrical:
I have not seen a machine that is loaded with HV fuses that can keep closing in! (you get this on LV). HV fuses are normally used to control secondary transformers and LV busbar faults.


My immediate thought was that this might have been an LV circuit that was fused at both ends and the fault did not clear the fuses, leading to futher explosions. Or maybe there was more than one joint in series and the joints failed one after the other.


If it was HV, then HV protection was severely lacking - an underground damaged HV should not be able to stay live. I'm sure the HSE will be looking at this very closely - somebody could have got seriously injured or even killed.
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