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Topic Title: "Many different reasons why the power goes off"
Topic Summary: Are we just 'unlucky' ?
Created On: 10 November 2010 09:39 PM
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 10 November 2010 09:39 PM
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keylevel

Posts: 477
Joined: 31 October 2003

We live in a smallish village (just over 200 properties) and have numerous power outages that last a significant amount of time (enough for the UPS batteries to run flat). We've lost the contents of the freezer a couple of times in five years and others have had equipment damaged after a long duration under-voltage event.

Power went off again at the weekend, so I called the emergency number to let the supplier know. At that time I also requested that their Investigations Team contact me to explain why we have so may outages.

They came back with a list of events from May 2010 onwards:

30 May 20:05 to 31st May 02:58 - power loss due to a wide area underground cable fault. Supply switched to generators with a further short loss of supply on 31st when repairs were completed and gen. sets removed.

21st Aug 10:24 to 16:38 - several short interruptions due to another wide area underground cable fault. Generators installed again and removed on the 24th.

9th Oct 16:33 to 20:22 - fault on wide area overhead network.

6th Nov 20:06 to 02:15 on 7th Nov - wide area network fault due to a plant issue at the local substation. Power restored after temporary repairs. 7th Nov 13:31 to 14:33 power cut to allow final repairs.

They conclude that "... power cuts were not due to recurring faults ..." and "... there are many different reasons why the power goes off and we cannot guarantee a completely trouble free supply".

Does this sound reasonable, or is it fair to say that the network in the area is a poor state of maintenance? Most of the long duration cuts we've had have been due to underground cable faults within the village.

What does "wide area" mean?

We also have a very high supply voltage - high enough to regularly trip my UPS into voltage reducing mode (highest recorded voltage was 260v using a Fluke 1653). When I reported this a network engineer was sent out and agreed that the voltage was out of spec and that something needed doing. Nothing has. I told him that it seemed as if the network in the area was in a poor state to which he replied "I can't comment on that"...
 10 November 2010 09:43 PM
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slittle

Posts: 3554
Joined: 22 November 2007

I live out "in the sticks" and we used to have loads of power cuts, to the point that I installed a generator (and we live on a small housing estate so you can imagine how popular I wasn't)

It's down to the lack of investment in the network by many of the DNO's I'm afraid. Not helped by the fact that we expect more and more supply to be available.

I would re-report your high voltage issue and keep reporting it until something is resolved.

Stu
 10 November 2010 10:10 PM
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alancapon

Posts: 5789
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It will depend on a lot of things. A voltage higher than the statutory limit (253v) should be sorted out. Depending on the number of substations you have, and for 200 properties, it could conceivably be one substation with a single high voltage supply, it may mean an outage for everyone while the tapping on the transformer is adjusted.

Low voltage is usually due to an 11kV overhead fuse operating, which will take just one phase out. The result of this is that one LV phase will be correct, the remaining two will add up to 240v or whatever the usual supply voltage is, and three-phase machines will not work. The vast majority of these fuses rely on customers ringing up to report a problem. From the DNOs point of view, the time taken will be dependant on how close the "on call" person is, and whether sufficient calls have been received to accurately determine the location where the fuse has operated from the Control Room, without having to visit several locations to see what has happened.

Underground cables can fail for many reasons. Paper/lead cables (PILC) can be damaged by stones or excavations, leaving a small amount of damage to the lead sheath. Water gets in, which can cause a problem after a minute, an hour, a day, a week . . . Usually, there is a flash-over in the cable, operating a fuse or circuit breaker. With LV, it is possible that the flash-over will dry out the cable without causing catastrophic failure. Often, the fuse can then be replaced, and there is no cost-effective method of locating the fault. Again, you are down to waiting while the "on call" person appears to fit a new fuse. We usually "try" a fuse in using test equipment to begin with, then take the power off again to fit a real fuse after a few minutes. This is a safety thing - you would understand if you tried to fit a 400A fuse onto a dead short without turning the busbar off first - LV fuses are usually fitted with the supply live.

Regards,

Alan.
 10 November 2010 10:23 PM
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keylevel

Posts: 477
Joined: 31 October 2003

Stu - I plan to keep pestering them about the high voltage - it could well explain why surge protectors and CFLs don't last very long here! They were due to install a long-term data logger, but that's not happened either.

Alan - Makes sense, as the under-voltage event was at the same time as an overhead HV fault. I don't envy the guys that get to 'play' live when things need fixing. Luckily some are brave enough

We are in a new part of the village and the supply is on a PVC (I think) cable. Most of the village is old, and I suspect the cables are as well. What worries me is that there have been quite a few failures, and it's PME - hopefully not a problem if it's flash-overs rather than joints.
 10 November 2010 10:25 PM
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hifly

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we are currently having 2 to 3 a month at the moment, every time it comes back on my fax machine prints a slip with the date and time on it. A couple more and i will be calling sse to get it sorted, mostly its loose joints on the overhead lines, so they tell me.

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 10 November 2010 10:35 PM
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alancapon

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Originally posted by: keylevel
. . . I don't envy the guys that get to 'play' live when things need fixing. Luckily some are brave enough

It can be entertaining, although it does load life insurance premiums a little! It has got a lot safer due to some of the testers. We carry "FuseMates" which are a fuse in series with a vacuum switch. These are operated remotely with a small keyfob, and give you 10 seconds to locate a safe place to stand. It does mean that if the fault is in the neck of the cable, it doesn't "let go" straight in front of you.

The HV fuses can be fun too - they are usually fitted live on overhead networks, using a set of insulated rods. Strong winds can add to the entertainment, as you need to bring the carrier to the ground for a new fuse element, then put it back up again. On a dead short, they go with one ******* of a bang. The sort of loud noise that makes all the local wildlife go quiet for a minute or two.

Regards,

Alan.
 11 November 2010 07:10 AM
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normcall

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We had that problem. The excuses ranged from 'residents don't like us to cut back the trees' to 'the local transformer blew up' (honest).

I got on the case in 1985, and this year we finally got all the overheads in the area upgraded to ABC. Naturally, our pole joint went up in a shower of sparks.
Alan, they use aluminium 35mm core with 16mm cooper braid round here - and leave the remains in our garden, still it was 1am when they came to fix it!

-------------------------
Norman
 11 November 2010 09:22 AM
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broadgage

Posts: 1308
Joined: 07 August 2007

My subjective impression is that power failures are becoming more numerous and more prolonged.

Some years ago, the lowest permitted supply voltage was reduced from 240 volts, less 6% down to 230 volts, less 6%.
I feel that many DNOs took advantage of this to declare an "investment holiday" In the past LV mains and the transformers feeding them had to be replaced/supplemented when the voltage become too low, but less need to worry now, it can drop to 217 volts and still be OK.

Stories abound of consumers asking for a larger supply, and being charged a lot of money for "network upgrades", when all that is done is to insert a bigger fuse in the cut out.

Whilst the supply industry may claim that it is getting better, I feel that they fudge the figures in many cases.

As an example a farm that I know has a 3 phase supply and used to have three single phase meters.
A three phase meter has now been fitted, with the result that if the supply fails for say 100 minutes, this is recorded as 100 "lost customer minutes" in the past it would have counted as 300 lost minutes.

I cant see things getting better, and would advise a large UPS or a generator.
UPS units are now very cheap, and can be fitted with external battery banks to give extended run times.
 11 November 2010 09:39 AM
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AJJewsbury

Posts: 11553
Joined: 13 August 2003

Don't talk to me about supply problems. I log every event that our UPSs complain about at work - about 36 so far this year and 13 in October alone. We're right next door to the substation and the small APC UPSs switch into 'voltage trim' most days (or rather nights) as the supply hovers around 253V much of the time. One set of light-flickering events was followed by a hole being dug in the pavement and an emergency repair overnight. Recently things seem to have calmed down since a YEDL van appeared outside the substation - so fingers crossed!
- Andy.
 11 November 2010 01:12 PM
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Ricicle

Posts: 843
Joined: 23 October 2006

Originally posted by: alancapon
The HV fuses can be fun too - they are usually fitted live on overhead networks, using a set of insulated rods. Strong winds can add to the entertainment, as you need to bring the carrier to the ground for a new fuse element, then put it back up again. On a dead short, they go with one ******* of a bang. The sort of loud noise that makes all the local wildlife go quiet for a minute or two.



Regards,



Alan.


A couple of times I have seen an overhead HV short at night. The night sky lights up almost like daylight. The first time I thought I was in a scene from Close Encounters.....

-------------------------
Empty barrels make the most noise.
 11 November 2010 08:04 PM
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chevalier

Posts: 61
Joined: 07 October 2002

The Distributor has kindly provided the evidence for you to claim a compensation payment under Regulation 11 of the Electricity Standards of Performance Regulations "...distribution system is interrupted for four periods, each of not less than three hours, during a relevant year. ..." =£54.

Money may not appear to substantial, but Distributors have to report numbers to Ofgem if continually highlighted they may prioritise improvements.
 11 November 2010 10:48 PM
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keylevel

Posts: 477
Joined: 31 October 2003

Thanks - I'll look in to this. The current paperwork doesn't detail four interruptions of at least three hours (only three), but there have been more in the months before.

If I can find four I'll get the Community Association to let all 300 hundred know that they can claim
 12 November 2010 12:57 PM
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OMS

Posts: 19747
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A couple more and i will be calling sse to get it sorted, mostly its loose joints on the overhead lines, so they tell me.


LoL - hardly suprising, I know of quite a few line crew who would tighten line taps to torque and then slacken back a good half turn whilst commenting they would be fine for a call out and a bit of overtime in a few months/years.

I guess things haven't improved either

Regards

OMS

-------------------------
Failure is always an option
 12 November 2010 07:42 PM
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slittle

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Joined: 22 November 2007

It's like Trees. There's a set of overheads on one of the farms that a big willow tree has grown towards.

We've asked and told until we're blue in the face to get it trimmed, I noticed yesterday the neutral (TPN) is now hooked around a branch, I'm saying nothing more to the client but I suspect they might make sure it's trimmed in the future


Stu
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