Solar PV system fault developed

Ectophile

It strikes me that there are two possibilities:

1. Your mains supply is over-voltage. As others have said, it should not be exceeding 253V (230V + 10%). If so, it's up to the DNO (Distribution Network Operator) to fix.
2. Your mains supply is close to the maximum, and the cable run to the inverter is too long and/or under-sized. When the inverter fires up, it pushes electricity down that cable into your supply. If the cable is too long or thin, there could be a significant voltage drop from one end to the other. You could have a situation where the supply is only 250V, but the inverter sees 255V when it is running flat out.

A good qualified electrician should be able to tell you.

countryman_2

Thanks for the detailed and very helpful and knowledgeable replys here. I'll check the grid voltage again tomorrow during the day, just to make sure then call Western Power Distribution (local DNO) if need be.

Yes it's rural out here but I'm within about 250m of an 11KV power line and can see the step down transformer on a pole at similar distance supplying about 10 homes.

I saw the inverter shut down at least five times today while I was in the vicinity and restart/shut down/restart but still managed 28Kwh. Definitely a nuisance I need sorting one way or another.

Martyn1981

Hiya CM. Best of luck with the DNO.

Just had a thought, any chance you could keep this thread updated with developments and any rules/regs etc that they quote.

I could then add an extra section on 'Grid - Over Voltage' onto the PV FAQs, and add a link to this thread.

I was thinking that whilst this issue doesn't come up too often, it's still important, and will only increase as more and more SSEGs are installed.

I'm sure somebody a year or two back said that DNO's are now getting 10x the number of high grid voltage reports due to PV installs. Not so much that PV is causing it, but because it was going unnoticed before. As I and bod1467 mentioned earlier, our 'pretend' 230V domestic grid, is anything but.

Cheers, Mart.

countryman_2

Will do Mart, all being well I'll contact them today and report back here as and when I have an update.

bod1467

Martyn1981 wrote: »

As I and bod1467 mentioned earlier, our 'pretend' 230V domestic grid, is anything but.

Quite. They may have changed the specified nominal voltage from 240 to 230. But they sure as heck didn't go around the entire network infrastructure and recalibrate everything from 240 to 230. Hence the fudge in the tolerances.

countryman_2

I checked the inverter twenty minutes ago and seen 259.6v grid, 226v PV. Interestingly the inverter is taking it in it's stride producing 3.2-3.7Kwh.
I rang Western Power and reported the high grid voltage and they have registered it as an emergency! Told me to switch everything off :exclamati and the engineer will be with me by 3pm and its almost 2:30pm now

They quoted 253v as being a maximum.

Martyn1981

countryman wrote: »

I checked the inverter twenty minutes ago and seen 259.6v grid, 226v PV. Interestingly the inverter is taking it in it's stride producing 3.2-3.7Kwh.
I rang Western Power and reported the high grid voltage and they have registered it as an emergency! Told me to switch everything off :exclamati and the engineer will be with me by 3pm and its almost 2:30pm now

They quoted 253v as being a maximum.

Question - if you switch everything off to prevent damage to electrical items, won't that push the voltage up slightly higher for other nearby households? Alternatively, it'll shut your PV system down, which might knock a volt or so off.

Oh well, at least they are acting quickly, and taking it seriously. Fingers crossed for a quick fix. :cool:

Mart.

countryman_2

Well, they were prompt I'll say that much, two of them, one in the meter box, the other up the pole(s) but would you credit it his calibrated Fluke meter (probes inserted at the meter) showed a maximum voltage of 253.7v that I saw. 251.5v with the leccy oven and kettle switched on. I checked the inverter and it was still showing 258/259v so perhaps the inverter is a little optomistic. Theier opinion was that 256v would be a maximum voltage out here which is very annoying to say the least.
They checked voltage and resistance (Megga) at the meter and several pole terminals in the vicinity using a Land Rover mounted cherry picker.
I told them there is clearly a problem and they have agreed to come Monday and install a voltage recorder which they may well leave for a week or even several to look for spikes (fingers crossed there will be some now), apparently if there are they have to turn off the 11kv and drop the transformer to a lower tapping.

I'll keep you all informed on progress.

Martyn1981

countryman wrote: »

I checked the inverter and it was still showing 258/259v so perhaps the inverter is a little optomistic.

Don't forget, the inverter will always be about 2V more than grid voltage so that it can 'push' the leccy into the house, and out onto the grid.

Apologies for the poor example, but imagine if you had water butts connected to the mains, then you'd have to pump them into your house at slightly higher pressure than the mains pressure, in order to use collected water instead of mains water, and to 'dump' the excess onto the water grid. [Note, in the case of water this would be illegal and dangerous. Just a silly example.]

Mart.

Martyn1981

"Section 14. Inverter shutting down, reporting overvoltage / Grid voltage too high."

added to PV FAQs.

Mart.