I just noticed the overvoltage indicator on my UPS going on and off every few seconds, so I stuck a meter on the mains. It's varying from 240 to 253V every few seconds. Any reason a mains supply would do that?
Sounds like an automatic tap changer in the supply authorities system has gone mental.
I didn't know they had those, is that how they keep the voltage so precise? It thought they had to have exactly the right amount of power stations active.
It's not changing that quickly, in fact it's quite a smooth change, like I'm running off a generator where the engine is speeding up and slowing down. It's done this a few times before over the past couple of weeks, but only for about 2 minutes then stopped. This episode has been going on for half an hour, although every 5 minutes it stops doing it for 30 seconds. I think I'll disconnect anything sensitive overnight and if it's still doing it tomorrow I'll phone them up. Do they spot things like this with remote sensors or rely on people noticing? There is a VERY slightly noticeable change in the brightness of CFLs and incandescents, but LED bulbs don't at all. I doubt anyone would notice if they didn't have a UPS with a warning indicator. I've phoned them before to complain about getting 255 volts, but they just said "That's within tolerance" - I guess a fluctuation is considered worse though.
Which might be the case if they have lots of taps and they're changing between them gradually? How many do they have?
Seems to have stopped now anyway. Now I'm not sure if I should report it or not.
Possibly or there is a fault that isn't a) destroying itself b) big enough to trip the protection.
TBH I'd go with an automatic tap changer or regulator having a hissy fit. The challenge now is to convince the DNOs Customer Service that you do know what you are talking about and it's a real, if weird, fault.
Our DNO, Electricty North West, normally respond to weird fault reports PDQ so if you call your DNO now you might find an engineer knocking on your door in a hour or two's time...
Yep. It's the only way to do that.
That doesn't work with the voltage at the end of the distribution system. You have to vary the tap uses as the load on that segment changes.
Likely the fault is just getting worse.
I'd do it now if it was mine, because its been happening for a few weeks and is getting worse. It likely won't be that easy to convince them that they have a problem tho and that you are capable of monitoring the voltage properly.
That varys with the system. Some do have remote monitoring, but most don't.
We had the entire town grossly over voltaged one evening as the load came off and the tap changer didn't do anything. The PDP9 has an entire column of fans up the side of the massive great door that holds all the logic cards. The whole column quite literally caught fire. Fortunately someone was actually using it that evening and turned the main switch off. Back in the 70s.
Yeah, likely.
Specially over that short a term.
It might be someone running something strange on you bit of the distribution system. Maybe someone has got the whole place turned into a cannabis grow house under lights just up the road or something.
Yeah, it shouldn't be very noticeable when it changes taps.
That varys with the design.
I would but like I said, you'll likely have problems convincing them.
Voltage varies locally according to the connected load. It could be a neighbour using something like an electric welder or large power tool. This causes a voltage drop.
It could even the be passing clouds affecting someone's PV panels nearby. My own + neighbour's panels drive the local voltage up around 10 volts on a sunny day.
You do seem to attract unusual problems recently from your posts. Maybe they ARE out to get you? :-)
Brian
Nar, it's just bad karma from what he gets up to with the cats and parrots.
Lights wouldn't go on and off like that.
I'll contact them in a moment....
Neither of those are likely between 11:30pm and midnight.
They might do if they are still setting them up.
True of most loads on your bit of the distribution system apart from a cannabis grow house being setup.
But is quite possible with a tap changer having a brain fart.
change,
I'm a little confused about how long it takes to go from 240 to 253 the 253 back to 240.
+1It'll also depend on where in the distribution the rogue regulator is. I think the steps @ 33 kV are 200 V which only produces a volt or so change at the 230 V level.
Aye, if the OP can log the supply volts at a suitable interval as measured by his UPS and produce some nice graphs to wave at the engineers when they call it helps. Also if you can read what the voltge is when they have their meter connected to verify the accuracy of the UPS readings.
Don't be fooled by some UPS voltage readings going to 1 decimal place though. My APC may say 240.5 V but the resolution is only 1.3 V, ie it will go 240.5, 241.8, 243.1 etc
people
Very much so, we had half volts after an ice storm did a lot of damage to the local distribution. Something woke me up and being half asleep got very confused as CFL's appeared to work fine, some wall wart PSU's where working fine, others were effectively off. When I plugged in an incandescent lamp it was *very* dim... I think at that point I got the voltmeter out followed by switching everything off at the CU and calling the DNO.
The upper limit is 253 (230 + 10%) but for them to really take notice it has to be above that for 10 mins or so. Gives time for the regulators to regulate.
Agreed. Our voltage is normally 240 V +/- 5 V 24/7, unless the local primary substation is being feed by the back up 11 kV line not the normal 33 kV one. There is a regulator at this end of the 11 kV backup but it struggles to keep our volts below 253 for hours on end at night. Last time the backup was used I managed to get someone to take "ownership" of the problem and emailled daily plots of the voltage as logged by my UPS. I think the information got to people that matter and that regulator was going to get a good looking at, it had struggled before. Now waiting for the next time the primary is on the backup feed but if they have fixed it tolerably well (so the UPS doesn't go into voltage reduction mode) I probably won't notice.
Another possibility is a high resistance joint in the neutral between you and the nearest substation transformer. When somebody else draws a high current this will cause your voltage to rise. This could produce the smooth increase in voltage that was reported.
It is definitely worth reporting, as such a fault could get much worse and be very destructive when it does.
John
But the voltage varied smoothly, if it was a load changing then someone was varying it gradually every few seconds to a precise timing, and the auto-tap changers weren't compensating. Now if I turn on my cooker full blast (oven, grill, all hobs), my voltage goes down by 1.5V. So for a change of 15V in another property, there'd have to be a huge load.
I emailed the electricity board, all I've got so far is "passed to technicians".
Yes, plug yourself back in, that might fix it.
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.