Please educate me on this one!

[S.G.]

It was 1975 when I completed my apprenticeship so I need some help with this query.(that's my excuse)
There was a power cut in our area due to the bad weather and when it eventually came back on I and my neighbours experienced the following:-
Dimmed lights, garage fluorescent lights wouldn't come on, Gas boiler wouldn't fire up or reset. electric hob would show power but not heat up and displayed a fault U1.Microwave would turn but no heat.
T.V,WIFI kettle all worked and having established that fault U1 on induction hob meant undervoltage I tried to find my old faithful meter but alas it was gone.
So I couldn't establish what supply was coming into the house.
Central heating firm I phoned for advice was convinced an internal fuse was blown or the circuit board in the boiler had been damaged due to a power surge.
Spoke to another retired electrician and he was none the wiser but was adamant that SWEB could not provide a reduced voltage to homes at a risk of causing damage to appliances etc.
Anyway 5 hours or so later power goes off for a while and when it came back on, as if by magic everything was back to normal. No evidence of any damage whatsoever.
Can someone please explain to an old sparky what has happened exactly and why and how the temporary power supply had such an effect.
Also what was that reduced voltage exactly?

 

[LarryFine]

Welcome to the forum.

It sounds like the utility provided lower voltage as a temporary fix while making repairs.

Of course, we can only guess.

 

[S.G.]

Welcome to the forum.

It sounds like the utility provided lower voltage as a temporary fix while making repairs.

Of course, we can only guess.

Thanks, but its bugging the hell out of me! lol
I can't help but ask, is this approved/common practice? If so what has been decided as an approved reduced voltage and why?
Should such utility firms (SWEB in my case) for-warn their customers of what to expect in such circumstances as no doubt many a gas engineer was called out on this occasion I bet!
Fingers crossed someone on this forum will have the answers for me.

 

[ramsy]

how the temporary power supply had such an effect.

Your profile location links to Wales UK, which uses a single 230v leg for domestic power.

How can half the appliances work on same leg, unless insufficient current, or voltage dropped, until power cut was fully repaired.

North American domestics get two legs of 120, where losing 1 leg is a common failure for 240v appliances to cut out, but we only lose half the 120v outlets.

 

[ggunn]

It was 1975 when I completed my apprenticeship so I need some help with this query.(that's my excuse)
There was a power cut in our area due to the bad weather and when it eventually came back on I and my neighbours experienced the following:-
Dimmed lights, garage fluorescent lights wouldn't come on, Gas boiler wouldn't fire up or reset. electric hob would show power but not heat up and displayed a fault U1.Microwave would turn but no heat.
T.V,WIFI kettle all worked and having established that fault U1 on induction hob meant undervoltage I tried to find my old faithful meter but alas it was gone.
So I couldn't establish what supply was coming into the house.
Central heating firm I phoned for advice was convinced an internal fuse was blown or the circuit board in the boiler had been damaged due to a power surge.
Spoke to another retired electrician and he was none the wiser but was adamant that SWEB could not provide a reduced voltage to homes at a risk of causing damage to appliances etc.
Anyway 5 hours or so later power goes off for a while and when it came back on, as if by magic everything was back to normal. No evidence of any damage whatsoever.
Can someone please explain to an old sparky what has happened exactly and why and how the temporary power supply had such an effect.
Also what was that reduced voltage exactly?

Only the POCO could say for sure what happened, but it sounds to me like they thought the problem was fixed and turned the power on, only to find out that it wasn't fixed, so they turned the power back off, fixed the problem, and then turned it back on.

 

[S.G.]

Your profile location links to Wales UK, which uses a single 230v leg for domestic power.

How can half the appliances work on same leg, unless insufficient current, or voltage dropped, until power cut was fully repaired.

North American domestics get two legs of 120, where losing 1 leg is a common failure for 240v appliances to cut out, but we only lose half the 120v outlets.

Thanks for taking time to reply.

 

[S.G.]

Only the POCO could say for sure what happened, but it sounds to me like they thought the problem was fixed and turned the power on, only to find out that it wasn't fixed, so they turned the power back off, fixed the problem, and then turned it back on.

Thanks....but we had 5 hours or so of this apparent deliberate ?reduced voltage.

 

[Seven-Delta-FortyOne]

In my area the POCO would never deliberately provide low voltage. If they did it would be accidental

I don’t know about your area. Nothing that you have posted so far would make me think they had done it intentionally, my guess would be a mistake that they eventually discover and repaired.

 

[ggunn]

Thanks....but we had 5 hours or so of this apparent deliberate ?reduced voltage.

How do you know that it was deliberate? Maybe the reduced voltage, if that is what it was, was a localized problem and it took the POCO five hours to determine where the problem was.

 

[S.G.]

How do you know that it was deliberate? Maybe the reduced voltage, if that is what it was, was a localized problem and it took the POCO five hours to determine where the problem was.

You are right I don't know but I strongly suspect it was a method used to keep the customers happy whilst working to find and repair the fault that took place.'
The electricity provider in my area in South Wales U.K. is Western Power Distribution and not SWEB as previously stated so I will endeavour to contact them when they are not so busy!

 

[ggunn]

You are right I don't know...

'Nuff said.

 

[Besoeker3]

You are right I don't know but I strongly suspect it was a method used to keep the customers happy whilst working to find and repair the fault that took place.'
The electricity provider in my area in South Wales U.K. is Western Power Distribution and not SWEB as previously stated so I will endeavour to contact them when they are not so busy!

Hi S.G. and welcome. I'm a Brit so we are on the wavelength but a Scot. As it happens have I spent quite a lot of in Wales, mainly in steel mills. Anyway I don't about your problem but I think it may have the temporary reduced voltage. That said, I have not experienced that - maybe Western Power had a glitch.

 

[S.G.]

Hi S.G. and welcome. I'm a Brit so we are on the wavelength but a Scot. As it happens have I spent quite a lot of in Wales, mainly in steel mills. Anyway I don't about your problem but I think it may have the temporary reduced voltage. That said, I have not experienced that - maybe Western Power had a glitch.

Aye...thanks for response I hope to speak with Western Power Distribution tomorrow or sometime in the week.
The many steel mills to which you refer have all gone from South Wales just like the coal mines....sad days!

 

[Besoeker3]

Aye...thanks for response I hope to speak with Western Power Distribution tomorrow or sometime in the week.
The many steel mills to which you refer have all gone from South Wales just like the coal mines....sad days!

Thank you S.G.
Yes, sad times. Few of the industrial plants I worked with seemed to have survived. Mostly pumping stations. But I have since retired.

 

[tortuga]

Your either fed from a delta - wye transformer or a two bushing single phase and the POCO had lost one of the primary phases or had a ground faulted phase.

There are old threads on that here:

Delta-Wye Secondary Voltages With One Lost Pri Phase

What are the secondary voltages (L-L, L-N) on a delta/grounded-wye transformer, when one primary phase supply to the transformer is opened, i.e. one fuse opens? Say a 12,470-480Y/277V system... Any references to published articles? Thanks!

forums.mikeholt.com

In a rural area you might be on a two bushing single phase transformer that is fed from two primary's (delta distribution with no neutral). When one primary has a phase to ground fault and the other stays energized you get an odd secondary voltage.
That happened here last summer at a house I was working on, something hit one of the primaries breaking it and grounding it but the other stayed energized. So the transformer went from a 12470 : 120/240 to a 7200 : 69/138 , I know there is also distribution like that in rural parts of the UK but you'd just have the one secondary voltage 240 and a different primary voltage and frequency of course!
Cheers.