Reply to: Long voltage reduction

[Archangel]

(dons brown overall)

I used to test the switches that switch 130kV supply at gec in the late 70's. Until we went on strike for months and I ditched it in favour of becoming a sparky.

(Removes brown overall)

[xoggoth]

F***! It's b*ggered my microwave fan! Unfortunately I tried to use it yesterday when I thought the supply it was back to normal, since the TV was working. Freezers/fridges seem ok fortunately.

[AtW]

Do they sell 3 phase sofas?

Yeah, mainly in the 40-watt range...

[AtW]

All fine here in Birmingham...

[suityou01]

Interesting, thanks. I've actually had this myself but didn't know it was phase related - I remember it well because our house was fine, but it transpired the fault was under our drive. So not only did they knock out our power deliberately, they were digging our drive up until 3am.

<<------ <ahem>

[vwdan]

This is then sent underground to your house. Still 3 phase. Every house in your street may well be on a different phase, that is you are on phase 1, neighbour on phase 2, neighbour +1 on phase 3. Then it repeats. So if in your street, on some neighbours are without power, this indicates a phase has gone. It does infrequently happen, I remember this happening as a kid

HTH AITIW

Interesting, thanks. I've actually had this myself but didn't know it was phase related - I remember it well because our house was fine, but it transpired the fault was under our drive. So not only did they knock out our power deliberately, they were digging our drive up until 3am.

[suityou01]

Yeah, I know he is only going to be single phase but the 1/2 voltage made me wonder if its further up at the distribution level.

Thanks for your question. And it's a fair one. Electricity is generated at source in three phases. That is to say, each 'winding' is at 120 degrees to the next. Each power station produces power on 3 phases, and each power station is linked to the grid. Each power station needs to generate power 'in sync' with the other power stations. This is computer controlled nowadays, but in the years of yore was a much more manual affair. Coupling a power station to the grid involved throwing some whacking great oil filled switches, with bloody great wooden prods. If they weren't exaxctly aligned (in terms of matching the revolutions) then it got 'interesting'.

The 3 phase is then distributed by step up transformers to the main pylon network, distributing at 130kv, then stepped down to 11kv and distributed by smaller pylon to your local substation. These are the buzzy grey boxes you see in the middle of the housing estate protected by chain mail fence with danger high voltage notices.

This is then sent underground to your house. Still 3 phase. Every house in your street may well be on a different phase, that is you are on phase 1, neighbour on phase 2, neighbour +1 on phase 3. Then it repeats. So if in your street, on some neighbours are without power, this indicates a phase has gone. It does infrequently happen, I remember this happening as a kid.

In Xogs case, they dropped the voltage across all 3 phases. Usually due to a supply problem, and I'm guessing the grid got damaged so they lost a power source (ie power station) to that part of the grid.

HTH AITIW

[vwdan]

Losing a phase only applies in 3 phase circuits, and would really balse up your PF correction.

Yeah, I know he is only going to be single phase but the 1/2 voltage made me wonder if its further up at the distribution level.

[suityou01]

Doom



Unlikely you are running induction motors, but the compressor on your fridge/freezer is now completely banjaxed.

HTH

PS Merry Christmas.

Undervoltage is very likely to screw fridges & freezers & not in a good way.

Most elektronicky stuff has very wide voltage ratings so isn't likely to get upset.

Spikes down the mains, however.

Yep. Next steps. Get an engineers report for fridge. Get an incident report from the lecky company.

Then submit your insurance claim. They will say they won't pay out for electrical failure. Then you tell them it's not failure it's damage. Then you get a derisory offer. Reject it and take the third derisory offer.

I realise it may not be worth all this hassle for the fridge itself, but the contents can run into £1000s

[suityou01]

I dunno either.

Being totally certified.

I wish they wouldn't do the straps on the strait jacket so tight, it makes typing with my nose a bit difficult.

Merry Christmas ole son.

[suityou01]

This - what you describe is highly abnormal. I'm surprised nothing has thrown a fuse yet, as they try and pull a higher current with the lower voltage.

It almost sounds like you've lost a phase somewhere upstream, but I'm not that up on mains electricity distribution. Are others nearby affected?

Losing a phase only applies in 3 phase circuits, and would really balse up your PF correction.

Where's the giant lizard, we need someone who knows what they're talking about I'm a bit out of date being only 16th edition certified.

[suityou01]

Doom

Commutated electric motors, such as universal motors will run at reduced speed or reduced torque. Depending on the motor design, no harm may occur. However, under load, the motor may draw more current due to the reduced back-EMF developed at the lower armature speed. Unless the motor has ample cooling capacity, it may eventually overheat and burn out.
An induction motor will draw more current to compensate for the decreased voltage, which may lead to overheating and burnout. If a substantial part of a grid's load is electric motors, attempting to reduce an overload by voltage reduction may not decrease load and can result in damage to customer's equipment.

Unlikely you are running induction motors, but the compressor on your fridge/freezer is now completely banjaxed.

HTH

PS Merry Christmas.

[suityou01]

Had a power cut about 8pm last night. Came back, sort of, about 1pm today. Electronic stuff like PCs work ok but anything with motors /heaters needing major power, the microwave, fan heater motors and electric hob don't. The garage door is very slow, more modern light bulbs work, older ones are half lit or flash. My multimeter says we have a US style 110V.

Seems downright dangerous as things are using energy but cooling fans will not run. Anyone ever experienced a long voltage reduction like this?

Yep. It's called a brown out. Equipment gets fooked. Insurance claim looms.

HTH

[mudskipper]

Shocking!

[xoggoth]

Had to turn PC off as was a burning smell, don't think PS fan was turning. Waited on phone 45m before giving up, useless *. Yet again just the same few houses had the same. Anyway, at 1.15 AM got up and all ok seems now. Great start to xmas. Grumble. Merry things to all at CUK.