Peculiar power outage

[Windmill]

A couple of days ago I woke at an unusual time, 5 a.m., to find that everything was dark and quiet. Realised that the power was off, and went to check the RCDs and breakers. All normal. Dug out a voltage-and-metal detector, and established that the incoming mains had no power.

This place was divided into two flats back around 1970, and utilities were rearranged to suit. The original owner must have worked for the electricity board, because he had electric room heating and thermostats in every room, which is probably why he had a 3 phase supply (did he get cheap electricity?!)

Now the upper flat is on one phase (and it had power though I had none) and the 'City of Edinburgh Stair Lighting' - a light in the entry - is on another. Both of those were still on. Just mine was off.

There was no reason to suspect that the main fuse had blown, but that had to be the most probable cause, so I called the supplier at 6 a.m., was asked if I would wait until 8 a.m. 'because we are busy', and said no. (Were they trying to reduce overtime wages, or had there been some kind of incident involving a number of homes?)

Found one circuit with a DC resistance of about 1 ohm, but later realised that was caused by a 240 to 110v transformer for power tools (and nothing there had tripped/blown).

The guy who arrived, quite promptly though he had to rattle the letterbox to get my attention (no doorbell, duh!), could find nothing wrong, replaced the main fuse, and everything has worked since then except that the 3 rate meter is delivering storage heater electricity on a timescale 45 minutes later than it should and once did.

I know of nothing wrong with the internal wiring except that one disconnected circuit has a neutral-to-earth fault. Allmost certainly caused by a socket I turned upside down to silence my mother's complaints that she couldn't get some plug or adaptor into it. This was about 30 years ago, and she had a habit of demanding I do something when I came back on holiday, even though I would have had no tools but a kitchen knife. Your sins come back to haunt you.

But as I said, that circuit was already disconnected.

So what caused the problem? Could the electricity meter have developed an internal fault? Could someone at a substation have accidentally disconnected the neutral line so that people on one of three phases got far more than 240V? Could that have caused the main fuse to blow even before any other fuses, breakers, or RCDs tripped?

Bit of a puzzle.

[charles]

[Snip]

sometimes fuses die of old age.

[Fredxxx]

Charles has already intimated that it could well have been a tired incoming fuse. That was my thought as well.

How old is this fuse? Even fuse-wire in cartridges oxidises leading to (premature) failure.

[Brian Gaff]

More likely it was just its time to go, perhaps. I remember some time ago a person down the road from me had to have the fuse changed and nobody ever did figure out what made it blow, as you say a surge or something maybe.

Are you sure no Skunk growers have moved into your loft? Brian

[Chris Hogg]

Two points. Our Economy-7 time clock does not depend on a continuous mains supply for its working AFAIK, i.e if there is a power cut, it carries on regardless. It's a mechanical beast, very like one of these

I assume either it's got some sort of clockwork mechanism that re-winds intermittently, or it has a battery back-up. So I would expect your time clock to carry on even with the main fuse blown.

Have you accounted for the hour change to BST when you say the clock is now 45 minutes later than it should be? Ours does not change when the clocks are changed, and the overnight low rate moves from 12 midnight - 7 am GMT, to 1.00 am - 8.00 am BST. If you haven't accounted for this, and your time clock doesn't change to BST, then your time clock is only 15 minutes out, which is well within the accuracy that these things are set up to, as they don't need to be set perfectly on time.

[Windmill]

It was a cartridge fuse. Might have been just 60A. rather than the more common 80 or 100 used today (I didn't ask). Might date back to when the three phase supply was first installed, maybe ?60? years ago, if electricity boards used cartridge fuses back then. Or it might date back to when the house was divided into upper and lower flats, around 1970.

There's a lot of cobbled-together electricity board stuff where the supply enters the house. Definitely very old. Scottish Power and their predecessor electricity boards didn't believe in fixing (or updating) what wasn't broke!

At 5 a.m. there would have been very little load, just one storage heater (I'm trying to keep down costs).

The original internal wiring was done to a very high standard for its day and I'm told that the MICC cable ( ! ) which carries the main load is pretty reliable.

Anyway everything has been working without a hitch since main fuse replacement, and someone is coming next week to reset or replace the

3 rate meter which is still 45 minutes late when turning storage heating on and off, although its clock is correct.

[Ash Burton]

It's unlikely that the meter was at fault or he would have replaced that too. It's also unlikely that there would have been anyone working at the substation at 5 a.m so i would discount that possibility. It does sound like main fuse failure due to fatigue.

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[ARW]

Other than pikeys:-)

It certainly does.

[Dave Liquorice]

The responsibility of the DNO engineer stops at the MET and outlet of the main cutout. The meter and tails from cutout are the responsibilty of the company you happen to be buying your electicity from.

So DNO engineer can't (shouldn't) fiddle with the meter unless authrised by the meter owner.

Was the "duff" fuse tested after removal and found to be open circuit? It or the clips could just have got tired or corroded. Changing fuse cleans 'em up.

[Dave Liquorice]

Ours is mechanical and the clock stops without power. It's currently about right but has been in cheap rate mode during the day for quite long periods of time. If the meter owners(*) can't be bothered to check the clock is correct I'm not going to tell 'em.

(*) Or rather their agents who come and read the meter on their behalf.

[Windmill]

The people upstairs are unlikely to be doing that. Rather conservative types with young children. Anyway it was just my supply; as I said they're on a different phase.

Having lived in Canada, I knew what a skunk smelled like, but it was a long time before I learned the reason that the odour could now be smelled over here, sometimes on buses.

[Windmill]

Here in Edinburgh the 'White Meters' have been electronic for a very long time and normally survive the occasional power cut without being affected in any way. Presumably there are internal NiCds.

This is an old Horstman meter (actuallly black in colour, though the newer, cheaper-looking meters have reverted to the original white) and the GMT/BST change is automatic. They can for an additional monthly charge be set up to allow Scottish Power to remotely control the on and off times for storage heating to suit the predicted weather, so I presume that the time change is also handled by radio signals (sent down the power line IIRC).

Originally the 'on' period began at exactly 23:30 and ended at 07:00 with another half hour top up in the afternoon to meet the 8 hour total on time which is guaranteed. (I have a neon indicator which shows me when the supply is on.) But since the fuse blew, the times are roughly 45 minutes late. I suspect that transients when the fuse blew have affected the electronics. And since it's a 3 rate meter (day rate/night rate/storage heating rate, all different so a little fancier than the Economy 7 which I believe is common in England) there's a risk that it will now be charging me incorrectly.

[Windmill]

I've seen fatigue mentioned, but never experienced it myself during a long life. Your reasoning sounds convincing though.

[Windmill]

Something which you guys would no doubt come across occasionally, but which I've never seen before myself, so that I half doubted the reports.

[Windmill]

Don't think so. His non-contact tester showed no power output.

You'd have thought it'd be difficult to get that effect, but I have a triple socket whose fuse does that.

[Windmill]

Having seen the repeated steep price rises, annual or more frequent, I sympathise. Wouldn't take that approach myself, but I had a rather Calvinist upbringing, some might say excessively so, and anyway my meter could be malfunctioning in any of the varied ways possible for complex electronic devices. (A 'White Meter' is capable of being radio controlled, though I didn't choose that option).

I called the supplier and someone is supposed to arrive Tuesday to reset or replace or whatever. And I'll be taking readings nyself and keeping an eye on my bills.

[Fredxxx]

Are you sure they're not using *your* supply?

[Windmill]

I doubt it; my bills aren't high enough for that ! Though I did find a cable which has power but doesn't seem to go anywhere, in my flat at least (just disappears up into the gap between plaster and brickwork where there's an air gap for insulation). Maybe a relic of the days when it was all one house?