80 V mains in Kerry!

Slightly Kwackers · 16-02-2022 6:57pm #1

Hi

I got up this morning to find that the lights wouldn't come on. Kitchen and one hallway were fine, but nothing in the other rooms.

All the none working lights were CFL or dimmable LED's.

Checking the Voltage I found it was 80V AC, before I measured the Volts, I had put the kettle on and used the internet, so the router was fine and the kettle did warm up, but when I found the problem, I turned it off.

The Voltage was back at 240 after a few hours, but why 80?

I cannot think why I would end up with a stable 80V. If it were a dodgy connection then the Voltage would dip when I cycled the kettle load surely? It didn't.

Not that it makes any practical difference, but can anyone account for that Voltage? Storm damage to cables or a transformer would surely be an O/C or S/C.

The only thing I can think of is a severely unbalanced supply, but surely this would be monitored for as a matter of course and the whole supply killed?

16-02-2022 9:41pm

It’s called a “brown out”. Contact ESB Networks.

Slightly Kwackers · 16-02-2022 10:26pm

https://www.boards.ie/discussion/comment/118643247#Comment_118643247

I did and the problem is sorted.

I used to cater for brown out's on remote sites, but the dips were normally of short duration and not so extreme. Brown outs would be minutes if that, any more and the instrumentation would have to have the data stored and recovered after the event.

I gather they were deliberately introduced years back to reduce loading, but this was down to 80V and the ESB were in attendance next door as well as in the village, so it would appear to be a direct fault on the distribution network.

Dropping a phase by more than 50% would be a very extreme situation. I was working at a place where a supply interruption of that order would see a couple of millions worth of damage.

That's what I was told anyway, it was an aircraft engine maintenance plant and yours truly did take the generator out a few times because the trip was too sensitive :-)

Nothing was on test at the time, but don't go up in anything driven by Pratt & Whitneys if the aircraft hasn't a very long, very secure mains cable :-)

16-02-2022 10:29pm

It is sometimes caused by loss of the neutral. Then you get “neutral displacement”.

L1011 · 16-02-2022 10:36pm

https://www.boards.ie/discussion/comment/118643559#Comment_118643559

Had this in Donegal before, ~60v and before the days of switch-mode power supplies being common so all we had was dim bulbs and the slowest kettle in the world.

80v and I suspect a lot of consumer electronics on switchmode would still work - like the OPs router.

Repaired as soon as ESB could get in - ferry required.

Bruthal. · 16-02-2022 10:43pm

Possible Neutral failure on the 400v network, or a phase down on the HT network.

Slightly Kwackers · 16-02-2022 10:51pm

https://www.boards.ie/discussion/comment/118643614#Comment_118643614

Yes, that would account for it, I was looking for the transformer but it was wet & windy :-)

The transformers used to be one per house but since they put three phase current on all the poles I don't know where the supply is dropped now.

I saw the odd tranny when walking the dog, they are stuck across a couple of the phases. I will have to look more closely.

Quite a large area was affected but there may have been more than one fault. A neighbour said the power was off for an hour, but mine was down for around four.

As you say, the switch mode stuff was o/k.

Slightly Kwackers · 16-02-2022 11:06pm

https://www.boards.ie/discussion/comment/118643679#Comment_118643679

Thanks, but I didn't think the supply came through with a neutral. There are three power lines all equally spaced on insulators, with the odd tranny dangling between a couple of the lines. I don't think any substations have appeared, they are well hidden if so. Three phase is newish though, it used to be a single phase feed on a pole with a tranny to drop to 240. That has gone, I don't know when, I must have been in the pub :-(

I fully intend to have a good look at the way the system works when I drag Pooch out tomorrow. At least everything is in view

zg3409 · 16-02-2022 11:15pm

Power was down to 86 bolts in parts of Wicklow town for 2 or 3 hours recently. They said there was a fire on esb transformer. Power went off then came back a few minutes later at normal voltage.

17-02-2022 1:38am

Yup it’s a brownout. A lot of electronic devices have switch mode power supplies that are designed to work across a range of voltages ~100 - 250V so will still work on very low voltage. LEDs will often light on very low voltages too.

Japanese power is nominally only 100V 50Hz (Northern Japan) and 100V 60Hz (Southern Japan) so there are plenty of mobile chargers and other power supplies that will be happy enough on 85V 50Hz.

Nominal voltage here is 230V as per EU/CENELEC/IEC harmonisation, but often supplies are still the old spec for 220V, so it’s often 220V +/- 6% or so in reality. We always use the continental European spec for voltage 220/380 now 230/400

In general, newer transformers and are aiming towards 230V so you’ll often see like 225-235V range. In general Irish power is pretty solid, well regulated and very stable. Long rural lines are long rural lines tho no matter where are.

British power was 240V (240/415V) spec, so you can get some very dodgy voltages U.K. at 256+ sometimes. Parts of Australia had a 250V nominal spec too which was kinda dodgy with 220-240V spec appliances. A slight spike and you’d issues.

General advice in a brownout is switch everything off. It can wreak havoc with some motors for example and you’re also at risk of a momentary surge when the fault it resolved.

Slightly Kwackers · 17-02-2022 2:27am

https://www.boards.ie/discussion/comment/118644475#Comment_118644475

Yes, we used to put timers in on UK rural equipment. A Voltage sensing relay would drop out and this would cause a complete removal of power, an interruption being better than a glitch inducing halfway house supply.

'Not sure of the procedure, I guess the transformers were tapped, but in the UK we had problems with high Voltage zapping electronics sometimes. [In the early days of semiconductors, transorbs were a long way off], so a call to the Electricity board got someone out to do a tweak at the substation.

I must say, when I tried the lights this morning, my heart sank, as the power appeared to be on, I had visions of a fault finding trip to the attic. This was not easy twenty years and around forty rolls of insulation back :-(

sparcocars · 17-02-2022 8:15pm

The answer to this is an MV phase was lost on whatever feeder supplies the transformer that supplies your house.

All of ESB's MV/LV trafos are delta star configuration so as a result there will always be a return path.

The voltage that would be measured at a three phase trafo that had lost an MV phase would be of three different values. One phase would have healthy voltage, one approx half voltage and then one approx quarter voltage. Whatever phase is the one after the healthy phase is the one thats lost.

Healthy R then S is gone.

Healthy S then T is gone.

Healthy T then R is gone.

If it is a single phase trafo that supplies your house then it was one of the two MV phases that supplies it that wad lost bacl on the three phase feeder and there was a return path through a three phase trafo.

Slightly Kwackers · 17-02-2022 9:48pm

https://www.boards.ie/discussion/comment/118648767#Comment_118648767

Thanks, spot on!

I suppose I should have been able to work it out, but it's a long time since I sat in college drawing vectors :-)

That would indeed account for the 80V

I was looking at the system today, they have quite long runs of two phases with quite a number of transformers connected, I would have thought the cost of running the three phases would not be so great and as I always had to be careful about balance, it seems odd to see the feed configured like this.

I suppose the ESB can handle the odd few Amps though :-)

Of course if everyone goes to electric cars, then I expect an upgrade will be needed fast.

The other plus point might be a chance to pension off my generator, which gets quite a lot of outings in this somewhat wild part of the country.

Thank you for the explanation, much appreciated!

Bruthal. · 19-02-2022 5:01pm

https://www.boards.ie/discussion/comment/118643819#Comment_118643819

The neutral failure was one possibility if there are multiple houses connected to the LV supply from a transformer, the other being a phase down on the high voltage side of the transformer, which is what i was saying with -"or a phase down on the HT network"- in post #6

80 V mains in Kerry!

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