Voltage question.

[Beelbeebub]

Quick question for those of you with grid PV systems and the ability to monitor their grid voltage..... 

 

What is the typical voltage you are currently getting?

 

Mine is the high 240's over the last 3 days. This is even overnight so I don't think it's just that there's alot of solar in my area. 

 

I was wondering if running so high (even without my export) was normal?  

[ProDave]

Almost all houses I have ever worked on have been over 240V

 

We "changed" to 230V some time ago but all that did was change the target with then a lop sided minimum and maximum tolerance meaning the typical 240V that almost every house receives is well within tolerance,  If you want to rule out voltage rise due to local PV generation, measure it at night when it is dark.

[Dillsue]

Well over 240v is perfectly normal. It's the DNOs way of getting more power to you by upping the voltage rather than the current. Our no load voltage is around 250v and tickles the max of 253v on a sunny day when the PV is going full chat.

 

The move from 240v to 230v was when we harmonised our voltage with Europe....they were at 220v and we were at 240v so we met in the middle

[ProDave]

42 minutes ago, Dillsue said:

 

The move from 240v to 230v was when we harmonised our voltage with Europe....they were at 220v and we were at 240v so we met in the middle

Just like we did not decrease our voltage, I bet they did not increase theirs either.  A paperwork exercise.

 

All it may have achieved is manufacturers design stuff to work over a wider range of voltages, which with most things using switching power supplies happened anyway.

[Beelbeebub]

8 hours ago, ProDave said:

Just like we did not decrease our voltage, I bet they did not increase theirs either.  A paperwork exercise.

 

All it may have achieved is manufacturers design stuff to work over a wider range of voltages, which with most things using switching power supplies happened anyway.

Pretty much this. 

 

My sorry is it limiting my export. 

 

Do they lower the voltage locally to allow export?

[jack]

1 hour ago, Beelbeebub said:

Pretty much this. 

 

My sorry is it limiting my export. 

 

Do they lower the voltage locally to allow export?

 

From memory, the DNO can change the local voltage by switching which tap they connect to on the local transformer. I'm sure there was a member a few years ago who was trying to get the DNO to do this but I don't recall the outcome.

[Dillsue]

1 hour ago, Beelbeebub said:

Pretty much this. 

 

My sorry is it limiting my export. 

 

Do they lower the voltage locally to allow export?

A higher supply voltage wont stop you exporting. Whatever your connection voltage is your inverter will raise the house voltage a little so power will flow out of the house and into the grid.

[Dillsue]

31 minutes ago, jack said:

 

From memory, the DNO can change the local voltage by switching which tap they connect to on the local transformer. I'm sure there was a member a few years ago who was trying to get the DNO to do this but I don't recall the outcome.

I'd heard that in certain areas, maybe with higher than average PV installations, that they seasonally change the tappings to lower the voltage in the summer and raise it in the winter. No idea if thats a fact or not but it seems logical to keep local voltage within limits.

[Beelbeebub]

So at midnight the grid voltage was 245v, but just after 4am (ie no PV generation in thr UK!) it peaked at 252.3

 

 

 

[Dillsue]

If you look at the voltage line through the night you can see it rises as everyone gets into bed and the load reduces. Around 6am the voltage starts to drop as people wake up and the load increases. As your PV starts to generate around 7 you can see the voltage start to rise and then drop off as your generation drops off. You can see your PV pushing the house voltage up as it generates. The rest of the fluctuation will likely be the load from you/your neighbours being awake and using stuff??

[SteamyTea]

1 hour ago, Beelbeebub said:

So at midnight the grid voltage was 245v, but just after 4am (ie no PV generation in thr UK!) it peaked at 252.3

 

4 minutes ago, Dillsue said:

around 7 you can see the voltage start to rise

Nationally, this is normal as more generation capacity is brought online, the Grid Operators predict what the loads will be and try to match that.

As mentioned earlier, increasing the overall voltage, more power can be delivered. Speeding up the rotational generators to greater than 50 Hz is one method.

This does not greatly affect local voltages.

There was some interesting work done on the affects of windspeed and temperature on overhead power lines, colder and windier weather means that more power can be pushed down the lines. Which coincides with wind farms generating more.

Generally though, our windier times are warmer. There is very good correlation between wind directions, windspeed and air temperatures in the UK.

[Kelvin]

Ours varies from 245V to 240V typically. Last night it peaked at 245V at 4am and it’s currently 242V with minimal PV generation. These values seem typical and yours seem on the higher side. 

Edited yesterday at 09:07 by Kelvin

[DamonHD]

FYI: https://www.earth.org.uk/note-on-16WW-mains-voltage-monitoring.html

 

I regard anything below 235.5V here as a sag, and stop diverting PV to my heat battery within 60s if so...

 

Rgds

 

Damon

[-rick-]

25 minutes ago, Kelvin said:

Ours varies from 245V to 240V typically. Last night it peaked at 245V at 4am and it’s currently 242V with minimal PV generation. These values seem typical and yours seem on the higher side. 

 

Depends where you are. I've not had a monitor for ages but did have (part of UPS) for a good long time in the past and I think 247V was nominal around here with it varying around that point.

[Kelvin]

I’ve checked it in a few different houses in various parts of the country and never seen it above 250V.

[Dillsue]

1 hour ago, Kelvin said:

I’ve checked it in a few different houses in various parts of the country and never seen it above 250V.

On a calibrated Fluke we're currently sat at 251v with minimal load in the house and negligible PV export as its grey and raining. A good chunk of PV export will push that to the 253v limit and a touch beyond at times!

[JohnMo]

1 minute ago, Dillsue said:

On a calibrated Fluke we're currently sat at 251v with minimal load in the house and negligible PV export as its grey and raining. A good chunk of PV export will push that to the 253v limit and a touch beyond at times!

It grey here also, but I am currently importing 5.7kW of free electric - thanks Octopus, charging battery and doing DHW next. Currently at 240V, 1 hour ago 247V, but does swing up to 250-251V, especially if exporting.

[Beelbeebub]

Thanks all. 

 

I'm just a little worried as my inverter shuts down if the voltage goes too high (253.6 for more than a certain time) - nothing dramatic, it just dumps me back to grid power - which is annoying as I then start consuming grid power even though my panels and battery are able to support me. 

 

Currently my export is set to 2kw limit pending the paperwork coming through for higher (waiting on installer). But the other day it threw some warnings and shut down briefly. 

 

It's nit the end of the world if I can't export much, though I do have a bunch to spare, but having the inverter shut down from time to time because the operators are running to close to the upper limit would be annoying. 

[DamonHD]

It is the DNO's legal responsibility to keep RMS voltage within bounds, as I understand it.

 

My dad's PV used to shut down occasionally from overvoltages, being on a semi-rural weakish feeder.  I believe that it got fixed.

Edited yesterday at 13:14 by DamonHD

[Kelvin]

It’d be more than annoying if it was shutting my system down due to over voltage. 
 

I might start tracking mine. While the inverter displays it as a sensor it doesn’t track it (just real time) and I can’t see that it’s exposed in Loxone or Home Assistant which is a pain.

[-rick-]

You can probably get a read out from a smart socket or a variety of other 'smart' devices. The smart sockets that can tell you power usage need to measure voltage.

[Kelvin]

Neither of the two types I have provide a voltage sensor. 

[SteamyTea]

What do multimeters, or other voltage sensing devices actually measure?

Is it peak voltage (V_p), the full voltage (V_p-_p) or the average voltage (V_avg).

When it comes to AC and power delivery, it is usually to use RMS values (root means squared).

The same is done with current.

When the two are multiplied together, the product is the DC power equivalent.

Edited yesterday at 16:24 by SteamyTea

[Beelbeebub]

3 hours ago, Kelvin said:

It’d be more than annoying if it was shutting my system down due to over voltage. 
 

I might start tracking mine. While the inverter displays it as a sensor it doesn’t track it (just real time) and I can’t see that it’s exposed in Loxone or Home Assistant which is a pain.

I've managed to get good data directly from mine by using a cUrl query and the parsing the reply. (SolaX). It's possible other brands can do the same, just a matter of finding the right query. 

[-rick-]

2 hours ago, Kelvin said:

Neither of the two types I have provide a voltage sensor. 

 

I assume you mean readable output. Just had a thought, do either of them have an ESPNow firmware you could flash onto them? If they don't monitor current/power usage at all, then ignore.