Mains power mystery (longish)

[Steve P]

At about 10.30 this morning I noticed several appliances in the house not working and lights were dim. On taking a meter to the main incoming supply I was supprised to find only 120-140V on the incoming supply. Asked next door neighbour if he was having problems but he wasn't and house opposite was OK as well! I rang Seeboard thinking my electric meter was faulty and they put me through to the main suppliers who took a fault report and said they would call me back (still waiting) at 16.00 I rang the main 0800 number and an automated announcement said they were aware of a fault in the Brighton/Rottingdean area. At 18.00 all power went off in the area and about 30secs later everything cames back on at full 240V. Rang helpline again and it stated "there was an overhead supply problem". Throughout the period of low voltage (10.30-18.00) the only thing that worked correctly was my 28in widescreen TV! I am assuming my TV can operate on any voltage from 110 to 240? As the whole estate is fed by underground supply how come neighbours were OK, I got 110V and the street lights didn't work at all?

Thoughts please?

[Stephen Dawson]

Easy, broken HV jumper of the high voltage network.

Steve Dawson

[Stephen Dawson]

To elaborate a bit more, the supply to your local substation was swapped from one hv feeder to another, probably to allow a repair to be carried out.

[tony sayer]

In article , Steve P writes

Possibly a phase "missing" on the high voltage overhead network?.

Yes most gear with a switch mode supply therein can operate well below the "nominal" operating voltage.

Are you certain that the neighbours were all OK and did U measure their supply volts?. Street lights possibly needed more volts than what were available to get started.

Do bear in mind that your underground estate supply will more then likely be fed via an overhead supply somewhere.

[Stefek Zaba]

Typically, adjacent house are on different phases - so a fault which affects just one phase (at your substation) will najjer the supply to roughly every third house. I don't know how in practice streetlight supplies are taken from the local substation - p'raps someone who does will pipe up real soon now ;-)

[Derek *]

Could it be that at various points around the town a single phase supply is handed over to the light dept who wire their own lampposts.

It won't be a very big load.

DG

[Newshound]

Fault just on one phase; you are on same phase as streetlights and voltage too low for them to strike?

[mike ring]

tony sayer wrote in news: [e-mail]:

So that's why my 32" widescreen telly doesn't miss a beat when my lights go very dim,(which happens frequently here just ouside the M25)

I often wondered

mike

[Frank Erskine]

I don't know how in practice streetlight

That's something I was wondering about whilst all the streetlights around here were being replaced :-)

[Ian Stirling]

It's probably not a good idea to use electronic appliances, even if they seem to work. While it may be fine to run the TV at 110V, some designs of auto-switching unit will have problems at 170 or so, and even if not, it's vastly more likely when there is a fault like this that you'll get spikes as it's fixed, which may kill what you're using.

[Stefek Zaba]

Dead right. Some years ago we lost quite a few PCs and workstations during an extended brownout/blackout/brownout cycling thang - apparently some of the "autoranging" PSUs were designed to sense what part of the world they were in, "locked" onto the idea they were in 110V-land when the voltage went low for a longer period, and then stayed "locked" as it came up to the full 240V. Whether that was an accurate description of the underlying mechanism, a simplified version, or pure bull - the fact remains that having gear connected while the supply voltage dances up and down is often a Bad Idea...

[Lurch]

On Sun, 09 Jan 2005 00:54:49 +0000, Stefek Zaba strung together this:

Another good reason for the incluision of a UPS by your treasured electronic equipment.

[Steve P]

I have now found out that my cordless phone with 2 cordless extensions has stopped working presumably because of power problems. Anybody know if the Electric Company pay compensation for damaged equipment?

[Lurch]

On Sun, 9 Jan 2005 09:37:37 +0000 (UTC), "Steve P" strung together this:

Sometimes, ask them.

[The Natural Philosopher]

I'd say a phase went on the overheads.

If your spupply was off 2 or 3 phases, then such a low voltage could occur.

[The Natural Philosopher]

Yes. I worked once on an industrial oscilloscope design that had a power supply capable of running off anything from 48v DC (aircraft apparently) to 250v AC. Just plugged it in, and off it went. No jumpers, nothing.

[Wanderer]

At a guess, I reckon Stephen Dawson most likely had the correct reason for the problem, although it might have been a tree bringing down just one phase of a high voltage circuit rather than a broken hv jumper. If you happen to live in a fairly remote rural location, it's quite possible that the hv protection failed to isolate the problem.

As to compensation, not unless you can show the company were negligent. Questions to ask are: 'When was the circuit last given a routine inspection? How often should the circuit be inspected? Is there any record on the line inspection data that might indicate there was a potential fault brewing? Is there any record of tree cutting needed anywhere along the circuit that normally supplies my electricity? What actually caused the broken jumper or conductor?'

Bearing in mind that we've had a couple of days of very windy weather, I think you've very little chance of proving negligence on the part of SeeBoard unless you can prove that there was a pre-gales condition that they knew about and failed to correct.

[Owain]

"Derek *" wrote | >I don't know how in practice streetlight supplies are taken from | >the local substation - p'raps someone who does will pipe up | >real soon now ;-) | Could it be that at various points around the town a single phase supply | is handed over to the light dept who wire their own lampposts.

It varies. In some localities, with overhead wiring, there's a fifth (additional to the three phases and neutral) wire on the poles, which is a timeswitched feed for streetlights mounted on the electric supply poles. Every 15 poles or so there'll be a rusty Venner timeswitch hanging off the pole.

In urban areas most streetlights will be fed individually on a single-phase tap from the local 3-phase. Illuminated bollards and traffic signs will usually be clustered on a switched supply from a streetlight which has a photocell switching the cluster.

If you've nothing better to do about 3.30 this afternoon watch the streetlights come on in batches :-)

Owain