PV solar cutting out due to grid over voltage in IP11 post code

Netexporter

I had a problem with wildly varying voltage tripping out my inverter. I had been monitoring the voltage, with a power plug, for a few weeks and on any day with clear sky the voltage would rise as the sun approached zero azimuth and trip the inverter when it exceeded the legal maximum of 253V.

I rang my DNO, National Grid, and they monitored my voltage, via my smart meter, for a few days. They agreed that the voltage was out of range and the next working day, about 6pm, they sent out a notification to say that they'd be switching off the the power to the area to carry out maintenance. I assume they did it at dusk so there would be no solar output, from any local arrays, to distort any measurements they took. Leccy was back on withing an hour and I now have only about a 2V variance around 240V, even on the sunniest days.

I don't know for certain what the problem was but I suspect it was a high impedance fault locally.

Anyway, top marks to NG.

Qyburn

JohnV6 said:

I can't see voltage on the smrt meter display.
In a power failure the solar shuts down as required by law.
We live on a newish estate. Last Mile Asset Management is our DNO.

What's the voltage you see on your supply when the inverter trips, and what's the voltage immediately after it trips. If the excess voltage is solely due to your export then your case with the DNO is weaker than if it's going over 253V even when your inverter is offline.

Does your G.98/G.99 agreement specify any voltage limits? Ours specifies that voltage at our connection point mustn't rise more than 6V as a result of out export.

JohnV6

Tracking it today even at 8:30 the voltage to export is 258. It seems to sit around 254 to 258 when exporting. At failure it is 260 to 262. The voltage then drops to 254 to 256

Netexporter

You'd best ring the DNO, not the local network owner, as that is way outside legal tolerances. They can then fight amongst themselves as to who fixes it.

Robin9

If you were to switch off the Solar what is the mains voltage ?

Scot_39

Good it did what it is meant to do.

The best you can hope for is their is say for instance flexibility at your local distribution transformer to say adjust tap points.

For DNO to create additional voltage headroom for feed in.

But in areas with higher solar installs - they might already have done so.

Solar export is not without disruption and should not be regarded as a right.

Nor should the pain be restricted to prevent new homes from benefitting up to a fair share of a sensible local limit.

And like other nations - UK solar at 5% of homes - with far higher local concentrations likely -  is becoming an increasing issue - so can see an increasingly restrictive regime change - caps below array / invertor sizes  - outright bans for new connections etc. - are in place in other nations.

Meaning solar increasingly for personal use - not export for profit at times when little grid demand.

During summer Agile so wholesale rates are near zero even negative on windy days - we pay grid level generators not to generate - time arguably we stopped domestic export and payments instead.  

1.4m even if only 3.7kWp basic 16A limit   - is still potentially 5GW - 20% of summer demand - it's too big to remain uncontrolled by regulators to match demand - given especially increasing risk and costs of of grid level renewables low demand so dont generate curtailment compensation payments.

The fact Octopus iirc dropped its day export rate by 3p on one of its deals recently - but increased its peak 4-7 rate -  is not without good reason when look beyond own meter, so  in the wider grid context 



 

MWT

Robin9 said:

If you were to switch off the Solar what is the mains voltage ?

That is the right question, and preferably coordinate with the neighbour to both turn off together and then see what the mains voltage looks like...

Qyburn

MWT said:

That is the right question, and preferably coordinate with the neighbour to both turn off together and then see what the mains voltage looks like...

He's said that after the inverter trips he's seeing 254 to 256V. I would argue the DNO is responsible for keeping that voltage within limits irrespective of what the neighbour is doing.

OP what voltage do you see overnight?

JohnV6

We had a power cut so zero & once the sun is gone the inverter sleeps. At 6:48 it was 250.8 , right now at 8:42 it is 256.8 

mmmmikey

Morning @JohnV6 just a quick thought and apologies if this has already been covered and I missed something.....

Is it possible that the inverter is measuring the voltage wrong, i.e. too high? That would have the effect of causing it to shut itself down (because it thinks the grid voltage is high even if it isn't) and also could account for the high readings.

Have you checked the grid voltage at the point it connects to the inverter and verified the inverter is accurately measuring the voltage?