Unexplained electricity cuts to our house only - HELP!

[Peter Boulton]

Hi,

We are getting power cuts to our house. They see to be associated with switching various pieces of computer kit on in the office but there is no consistent offender, and all the kit has been running perfectly in the past.

The odd thing is that none of the consumer unit thingies trips, it affects the whole house, the disc stops in the meter and anything from 5 mins to an hour later the power magically comes back. Also, the lights start to flicker just before it goes completely. Even of they were on and constant up to that point.

We've had the electricity supplier out a couple of times, but sods law is that the power was back when they came and they couldn't find anything. They measured the voltage at the meter for a couple of minutes and said it was fine.

Possibly irrelevant, but in July we had a new boiler put in, relocated from another place in the house so there was a fair amount of electrical work. The electrician said the house earth reading was way too high and the power supply company came and did something out on the pavement to restore the earth reading to close to zero.

I have 'caused' a cut when the boiler and central heating master electrical switch was off.

I just don't understand what's causing the whole house to lose power, and also what's causing it to then spontaneously come back a few minutes to an hour later.

I'd be very grateful for any suggestions or ideas on what it can possibly be. (I've got an electrician coming tomorrow lunchtime, but the work is piling up and every time I start the computer the power goes again! I do have a UPS, but the spikes (or whatever) when the power is going seem to cause it to shut down immediately.

Thanks!

Pete

[The Natural Philosopher]

You have an intermittent connection in the supply =- almost certainly upstream of the meter.

Possibly there is a thermal fuse in your supply, and thats going on and off. Or a dodgy cable. Or connection.

Ahem. Here is a thought. I had a digger slice my underground. Occasionally it would blow the fuse at my (yes, I am its sole supplier!) substation (a large box at the bottom of the garden). The chaps came out and replaced it twice, and it blew again. The next time they said "sod this: There's a 150A fuse in there now. The next time it will blow the cable where is shortin and we will know where to dig"

It did, and they did.

SO..if your nerves are up to it, short the supply to your house.

That will blow whatever is dodgy PERMANENTLY and you can get it replaced..

Its not inside your house. Or at least its upstream of your consumer unit. Which is the limit of technical competence for your electrician. Its the supply companies purlieu

If you want to pursue the legal and orthodox, insist that your power company fit voltage recording to the METER. That will show that its happening at that point or further upstream..

[Dorothy Bradbury]

There are (often) link disconnects in the pavement... o These trip at 300A as I recall

---- however I thought they covered 2-4 houses o They automatically reset

---- a few seconds after the fault has cleared

---- I suspect simple bimetallic link in a box

So it could be an underground cable fault somewhere.

Fault may be closer if you are on a loop-in service cable. o Neighbouring houses are often looped-off another

---- one house gets a service cable from the street

---- neighbour house gets a loop-in off your service cutout o If your cable is a loop-in it may be a fault there

---- the neighbour service cutout may have a fault

---- yours or theirs may smell, or be hot

Verify also your CU is not running hot, smelling or during the flickering you can detect nothing either. Important to verify it is not "your side of the meter". Up to the meter is the supply companies responsibility

This is a real risk to your equipment... o Flickering lights indicate a potential surge

---- power is on/off/failing/on/off o Surges like this kill devices quite easily

---- electromechanical timers seem to go first

---- surge protectors in washing machines next

---- microwaves & PCs come up next

IIRC supply companies do not provide compensation for surge damage - verify your house insurance does.

Many supply cables are PILC, Paper Insulated Lead Covered. The paper is oil impregnated, if it cracks or splits the oil can drain down and it will fail. Without a link disconnect box in the pavement the full PSSC current can flow (which can be 16kA) and the result will be a large cone shaped crater and a loud bang. With a link disconnect box a shorting service head will make an big bang - but take out several houses.

So it is perhaps odd that no other houses are affected. I assume street lights & other houses do not flicker?

The supply company can fit a logging meter. This will log the supply voltage, once you find a flicker or cutout, they will examine the records. It will show if it is "their side of the meter" (supply) or whether it is your side of the meter.

If you have a whole-house RCD there is the chance that it is faulty - but you say it does not trip. So that can probably be ruled out - ask for a supply log.

[Peter Boulton]

Thanks! Please excuse my ignorance, but when you say 'upstream of the consumer unit' do you mean on the house end or the bit between the meter and the street/main power supply?

All the best,

Pete

[Mathew Newton]

Just in case you were tempted, ignore this absolutely stupid advice.

Mathew

[Peter Boulton]

Thanks Dorothy! I follow some of it! :-) Unfortunately the neighbouring house one side is unoccupied and the other side is old folks flatlets with a generator. I suspect it's just our house. We live in the sticks and have no streetlights!

The CU isn't hot.

I had a cheappo surge protector 6 way adaptor, the one with a red and green light, where green means surge protection enabled, but now the green light is very dim - guess it's been taken out.

My UPS for the computer shut down, as I said, when the mains appeared to be spiking badly but seems OK still (if I just switch the power socket off while the computer is running). (Why doesn't the CU trip in these cases?)

I'm currently powering it via an extension reel from another room in case there's a problem with the socket in my office. We've had just one set of light flickering during that time. Not that that means anything - it's gone fine for a few hours before and then it's been terrible.

Thanks again!

Pete

[Rumble]

On the supply company's side of the meter, i.e. between the meter and the street (and indeed all the way to the substation).

As others have said, it sounds like there is a fault in the cable between your house and the substation. (The following is based on what happened to me and about 20 other houses in my street a few years ago)

If there is a cable fault in the street which allows water in, current will flow to neutral or earth in the joint causing a "brown out". In this event the lights will dim and flicker and if the brown-out lasts long enough, your computer might reset, etc. If the fault current is high enough for long enough, then one of two things happens.

1. An automatic recloser is activated. In this case, the auto-recloser trips and power to your house stops. After a sort time, the auto-recloser reconnects the power and power to your house comes back. Often, the heat generated by the fault current in the street dries out the joint for a while and the problem doesn't come back until tomorrow or next week.
2. The auto-recloser has tripped three times and/or a (300A ish) fuse has popped in the sub-station. In this case, the power will be off until an emeregency call-out person attends the sub-station and manually recloses the auto-recloser or changes the fuse. In your case, it takes the electricity company about an hour to get someone out from the depot to your local substation. Again, the fault current will likely have generated enough heat in the dodgy joint to dry it out and make the problem go away for a while.

In either case, the only permanent cure is to dig the pavement up, find the dodgy joint and replace it. If the local records are incomplete and/or erroneous, then the electricity company will not know where to dig the pavement up (i.e. they don't know where the joint is or they don't know there is a joint at all). However, after a year or two, the pavement will start to collapse where the water is seeping into the joint and it will become clear where they (and often the water board as well) have to dig to fix the problem.

HTH

[The Natural Philosopher]

How is the supply coming in? from pole or undergrund?

[The Natural Philosopher]

I mean anything from the fuse/switch box back towards the supplier. Including the meter.

Your responsibility starts at the meter IIRC.

[The Natural Philosopher]

I'll pass that back to the power company that suggested it then..

[Dorothy Bradbury]

Why do they have a generator?

[Mathew Newton]

[James Salisbury]

Hi, In order to help find where the problem is and totaly remove your side from the equasion you need a live wire detector. Pop into B&Q and buy an MK live wire detector this will bleep and show a red light when it is near something live. Practice with it and note where it lights up when placed near each of the 4 cables connected to your meter. Repeat the exercise when the mains has failed. If there is a difference then call the eletriciy company..

[The Wanderer]

The only way to try and find out what is wrong is a logical, step-by-step approach. Don't pay too much attention to some of the misinformation that's already been posted.

Are you certain that you're the only place affected?

Whereabouts in the country are you?

Do you live in a town or a rural location?

Do you know if your supply comes into the property by underground or overhead cables?

Have you actually lost electrical equipment as a result of these incidents? It could help determine if the fault is on the high or low voltage systems.

Are you sure it's as much as 5 minutes? Being without electric can seem like ages when you're in the middle of something.

The 'short' time you describe sounds very much like the time delay for an automatic reclosure of high voltage switchgear out on the system.

Is there any chance it could actually be between 30 secs and a minute, which are typical times for reclosure?

The longer time suggests human intervention with the reclosing of a switch somewhere, although most switchgear these days is capable of remote operation. The local distribution company will actually have written records where human intervention occurs, unless things have changed that dramatically! Unfortunately, you'll have one hell of a job on your hands trying pin down someone at the right location, given hoiw much consolidation has gone on in recent years.

It also suggests you are in a rural or mixed urban/rural location. Entirely underground hv systems don't usually have an automatic reclosure after faults. This is because when a fault happens on underground systems they're almost invariably sustained faults.

It's only where overhead high voltage systems occur that transient faults can occur, like swans flying into and clashing the wires, or a branch blowing up against a live conductor.

That sounds very much like the lead in to a fault where the actual fault current isn't that high.

Unfortunately, since the industry was privatised a couple of decades ago (was it really that long?) a lot of the expert engineering knowledge was lost. Too much concentration on the bottom line of the balance sheet! The one thing I'd be fairly certain about based on what you've said is that it ain't in your property.

[The Wanderer]

And what exactly will that tell him? Just out of interest, what would you expect to see if the polarity is reversed, or even worse, there's neutral inversion?

[Steve]

Yes, totally stupid and irresponsible to suggest this, especially as the short would have to be made on a live supply before the house's main fuse!

Perhaps the Natural Philosopher should explain how he would go about doing this safely and without interfering with the supply cables, and why such an action could be suitable for a DIYer who is concerned about power cuts.

This has to be the worst advice ever on this newsgroup.

Steve

[James Salisbury]

It will show if there has been a change when the power goes off. Just to confirm that the supply has a fault. If there is an up stream live open cicuit then nothing will show. If the neutral has gone oc then all will apear live.

[tony sayer]

Any suggestions for the average D-I-Y'er on how to do that!!!....

[dom]

Does power come to your house on overhead wires or underground?

If overhead, a prowl of the neighbourhood for trees touching wires, cables so slack that they can touch on windy days etc may give clues.

Surprisingly, when I reported storm damage to 11kV wires, I got to talk to a techie person and gave them detailed info including a gps location. They said that detailed reports tended push things up the priority list enough to send a repair team, rather than leaving it until their own scout had been.

[Peter Boulton]

Because power to our village has historically been unreliable and the flatlets are attached to an old folks home. (Old folks have a habit of passing away when it's cold and their relatives pay a lot of money to the old folks home!) I take your point of course, but in this instance I don't think my problem is related to the historic poor electrical reliability in the village, which is much better in recent years anyway.

Having said that, we're only 30 miles from the centre of London, not the Outer Hebrides!

Pete