What's your average single phase measured voltage? Is 251V at point of measurement common?

[eveares]

So to set the scene, my elderly grandparents live in the rural Kent countryside and have had a APC UPS for a while as they live out in the country and get a fair few power cuts, and not only their internet/router but also there landline phone depends on the mains power being it's a VoIP landline phone.

Hence being their landline phone relies on the mains powered router working and they get poorish mobile reception, installing a small UPS for them a few years ago seemed like a good precaution in case they ever need to dial 999 when the mains power is out.

Today I installed a small Raspberry Pi to monitor the existing UPS and send me emails when the power goes out. What I was a little surprised about was the mains input voltage reported from the UPS, being 251V at one point. Of course this on the upper end of the nominal 230V +10%/-6%, and was just wondering how common this is in the UK to have a voltage measured as 251V at a socket receptacle?

Now of course I did not have any of my other gear (MFT1730, multimeter, plug in power monitor, etc...) on me to cross check what my UPS was reporting voltage wise and I know it's not a officially calibrated device, but it's the highest that I have ever seen in person for a normal healthy single phase voltage in the UK.


Curious what peoples rough average voltage is where they live at. Of course this is going to vary depending on things like the total load, impedance of cables, phase imbalance, etc... causing voltage drop, but curious on what people's rough average voltage at home is. Mine in East Surrey is around 235v give or take a volt atm. Was 243v from what I recall a number of years ago.

Regards: Elliott.

 

[JohnW2]

Curious what peoples rough average voltage is where they live at. Of course this is going to vary depending on things like the total load, impedance of cables, phase imbalance, etc... causing voltage drop, but curious on what people's rough average voltage at home is. Mine in East Surrey is around 235v give or take a volt atm. Was 243v from what I recall a number of years ago.

In my house the average is usually around 243 V - 245 V, very rarely below 240 V or anything like as high as 250 V.

As you say, it depends upon many factors, primarily proximity to the transformer/substation and the total load (of all consumers) on the phase. A family member of mine lives only a few meres from a 'substation' and her voltage is usually around 250V, whereas I would imagine that those at the far end of the cable run will usually have much lower voltages than that. The supply voltage is obviously 'allowed' to be anything between 216.2 V and 253 V.

Kind Regards, John

 

[Harry Bloomfield]

When I could be bothered to measure it, it was always very close to 240v. We are 100yds from the sub..

 

[hovertoast]

I often see 253 late at night. We’re about 350m from the transformer, and looped from next door. Often see dips to 230, it’s noticeable in the summer with a fan on as you hear the pitch change.

I’ll get some pics of my cheapo plug in meter.

 

[Why Not Indeed]

Varies throughout the day. I reckon the Solis inverter is more likely to be accurate than my Shelly EM, but the inverter is only on when the sun is shining.

 

[ericmark]

I have just looked

and I get this, but it does not log voltage over time.

 

[JohnW2]

I often see 253 late at night. We’re about 350m from the transformer, and looped from next door. Often see dips to 230, it’s noticeable in the summer with a fan on as you hear the pitch change.

Interesting. The dips to 230V are not surprising if you're that far from the transformer, but if you often get 253V athat far from the transformer, one would expect those close to the transformer to be getting well over 253V (the theoretical 'maximum')

 

[SUNRAY]

Interesting. The dips to 230V are not surprising if you're that far from the transformer, but if you often get 253V athat far from the transformer, one would expect those close to the transformer to be getting well over 253V (the theoretical 'maximum')

That was a problem atmy first house, the sub fed the whole streetand I was the first, being number 73 there were eith 36 or 72 more following on. While I renovated it I was getting through light bulbs like they were going out of fashion and often had 260-270V. Complaining to SEEBoard they fitted a pen recorder for a week with a scale of 200-300V which revealed several incidents of spikes over 300V. The supplied a box of 25 assorted rough service bulbs which lasted for years and eventually they added another cable to fed from the other end.

 

[hovertoast]

Interesting. The dips to 230V are not surprising if you're that far from the transformer, but if you often get 253V athat far from the transformer, one would expect those close to the transformer to be getting well over 253V (the theoretical 'maximum')

Yes, agreed. I suspect that the highs are due to being relatively densely populated area and the lows are when next door run something high power at a peak time (i.e. large drop across our shared cable when the voltage is already low).

I will get pictures to demonstrate.

 

[chivers67]

In my line of work in Highway maintenance I often see Voltages in excess of 250 Volts. They do tend to be in rural areas fed via poles. occasionally when too high I have to report it as some equipment are effected by the upper tolerance

 

[ebee]

Well, once upon a time 240v =/- 2.5% might have been a useful target and now 230V +6%/-10% might be more useful target now but if ideally you have equipment that is unlikely to suffer much from 230v - 10% to 240+10% for much of the time you might be better off too.
You need to consider, will it cost more and is it worth it, what can happen at worst and do I really need to mitigate against it.
Do we need to make it bomb proof or can we accept the risk - filament lamps were a good example of things and the extra for "rough service lamps" might have been a good choice in some circumstances.

 

[Harry Bloomfield]

The supplied a box of 25 assorted rough service bulbs which lasted for years and eventually they added another cable to fed from the other end.

'Rough service', being just lamp bulbs, where the filament is just better supported, and slightly under run - so less light output for their consumption.

 

[fixitflav]

Does anybody know whether "modern" lamps - LED, halogen etc or even fluorescent, are more or less tolerant of under or over voltage?

30-odd years ago buying a bulb was straightforward, nowadays there's a huge choice!

 

[JohnW2]

Yes, agreed. I suspect that the highs are due to being relatively densely populated area ...

I'm not sure what you're suggesting there - perhaps that they set the supply voltage at there transformer to as high as possible in a 'highly-populated area'? They really should keep that voltage low enough that the consumers closest to the transformer don't get more than 253 V.

and the lows are when next door run something high power at a peak time (i.e. large drop across our shared cable when the voltage is already low).

It's not just 'next door' the current going to every installation downstream of yours will go through the 'shared bit of cable' (between your installation and the transformer) that determines the voltage drop between the transformer and your installation.

 

[bernardgreen]

Most are less tolerant. Cost cutting design being the biggest culprit.