Is the system v close to a substation/transformer and thus mains voltage *is* at the top end of the range? (If so the DNO may be able to tweak it downwards I suppose.)

Has the inverter been left on the settings for the wrong country (eg German) with slightly different voltage limits? If so the installer should fix, possibly requiring a magic code from the manufacturer to switch regions.

Is the AC wiring from inverter back to consumer unit too thin, thus letting the voltage rise too high? Does that wiring get warm to the touch?

Rgds

Damon

If it's in spec then the inverter should cope, I imagine.

For a friend's installation they were right next to a substation and right at the top end of the acceptable range, causing some trouble to the inverter, so the DNO tweaked the voltage down a tad, and all was well.

Rgds

Damon

PS. A plug-in power meter may do a reasonable job of reporting volts RMS.

Posted By: CWattersIt's an interesting topic because it implies there are some sites where PV can't be installed because the grid voltage is too high. Not sure what they do in such cases. Who pays if the mains voltage is high but within spec?

AIUI, you're allowed to source up to 16 A and it's still the DNO's problem to keep the voltage within limits. They can ask you to temporarily disconnect while they sort it out but any changes to the network to do so are at their expense.

However, that'll presumably be based on the voltage measured at your main fuse. Any voltage drop beyond there would, I imagine, be your problem. I think the moral is that if your voltage is at all on the high side then put the inverter close to the main fuse.

Posted By: Ed Davies AIUI, you're allowed to source up to 16 A and it's still the DNO's problem to keep the voltage within limits.

Thanks that makes it a lot clearer.

Max they should supply is 253v - not sure if they can go above this very occasionally, but it seems you have a pretty consistent over voltage. Most inverters for the UK market are set to cut out if the supply goes above 253v or below 216v. If the DNO supplies high volts then your bills will be higher.... . We also discovered that laptop computer switched mode power supplies will set off the RCCB trip if the voltage is very high. We had terrible problems with them until the voltage was reduced to 235.

Power is power: the voltage at which it is produced or consumed is irrelevant for these purposes. You can't break the laws of physics (unless you have Tony's dispensation) and magic more from the system with the same sunlight coming in just by virtue of the mains voltage.

Rgds

Damon

But if the voltage is higher you can feed in more power while staying within the 16 A limit.

Not that, as understand it, any of the inverters allow you to set the current limit, just a power limit.

Just a quick update on my original problem...

The DNO are still looking into the problem. They did come out at 6 on the day I reported it and said (I paraphrase) "It measures 249V so within tolerance". I pointed out that the village is on a spur and that at 6 in the evening I'm not surprised the grid voltage is within tolerance as everyone's drawing. Also it fluctuates by 10V throughout the day anyway. Called them back and they are now taking it more seriously. The guy said they are getting no end of calls since the rapid takeup of PV. They're talking about turning down the tap 2.5% but I guess they need to do some tests at the bottom end of the spur first.

I wonder what other options they have if the bottom of the spur is close to the low end of the range? Presumably they are obliged to come up with a solution (voltage regulator before meter in my garage maybe?).

I'm a bit dissappointed that this assessment of grid voltage does not form part of solar pv design or atleast the commissioning process.

To their credit the Solar installer did came out to recheck the setup and identified that the box was still set for Germany - and they need to apply for a code for the UK. I don't think this is material in terms of the cut off function, but it just goes to show how careless Solar PV installers can be. Again inverter set up should be part of the commissioning process.

Posted By: DamonHDI think the German range is tighter:

Is that why there are concerns in Germany about the grid mix and the large uptake in in PV.
And it must be remembered that one scheduled shut down of a cable in Germany caused a cascade of unscheduled ones across mainland Europe.

Posted By: DamonHDI think the German range is tighter

At both ends of the range. or just at the upper end?

i.e. could the UK v Germany differences just be a side effect of the harmonisation of voltages to nominal 230V which (so far as I'm aware) didn't involved any actual changes to the networks, working instead just by allowing generous enough +/- margins that existing national systems were okay as there were?

Just a thought...

skyewright: I don't know, but at a WAG, the top end would be more likely a problem given the sleight of hand in the 'harmonisation' that you refer to.

Rgds

Damon

An update...
I'm still waiting for SolarTech to come back with the override code to change seting from German to UK. Also DNO are planning to get the hot glove team to turn the tap down 2.5% in the new year. System is still cutting out. But hopefully will work fully by mid Jan.

Mark.

Update.

The DNO (who were very professional) came out just after Christmas and turned the tap half-a-screw. This has resulted in voltage remaining within range. Max now of 250V, but generally around the 240V mark. I'm still waiting for code to set inverter into UK mode though, but don't think this is material to my problem.

This seems to have resolved the original problem. Performance on a good sunny day at this time of year results in 4.5 to 5.5kwh. So far very pleased with it as its only a 2.5kwhp system, it is only Jan and there are some trees which block the low sun in the afternoons.

<blockquote><cite>Posted By: Phil.Chaddah-Duke</cite>Is that a peak of 4.5 to 5.5Kw out of a 2.5Kw system? That's pretty impressive, wonder if there is still something wrong with ours! Where is the installation and what kind of panels are used?</blockquote>

Looks like 4.5 to 5.5 kilowatt hours for a whole day from a 2.5 kilowatt peak PV installation to me.

Daylight hours are around 8 hours at the moment, so 5.5 kWh equates to an average power from the 2.5 kWp PV system of around 0.69 kW, or about 27% of peak power.

Mmm, just under 6.5kWh from mine yesterday (and just over 2kWh today).

Rgds

Damon