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DNO voltage limits and solar PV generation

A local bowls club has installed solar PV which is working very nicely - most of the time.

However on a really good day up to 8 of the 53 panels trip out reporting overvoltage. The trip is set to 264V (240V + 10%).

The meter is in a small house at the edge of the property, about 50m from the main switchboard, connected by a fairly substantial cable, (at least 2 sizes bigger than the DNOs incoming cable). We have called the DNO who have been and measured the incoming voltage as 252V, so just below the limit of 253V (at the time of their visit).

Exactly how the voltage rise is distributed between the incoming cable and the cable from the MCB board to the roof isn't clear but the voltage at the MCB board is regularly above 253V and so is the voltage on any appliance connected to a lightly loaded circuit.

The DNO say they can monitor the voltage but unless it goes above 253V they will not reduce the voltage as it is within limits.

How can the club ensure that their equipment is not subject to over voltage?

Do the DNOs limits need to be reviewed now that electricity flow to a premises is not always in the same direction?

0 Alan Capon over 4 years ago

Ok, well at 15kW it should be a G.59 connection, where the inverter settings have been agreed by the DNO for that specific installation. The standard “off the shelf” for G.83 connections are limited to 4kW. I am of course assuming it was notified correctly . . .

Regards,

Alan.
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0 Sparkingchip over 4 years ago

Sparkingchip:

And if there’s more producers than consumers on the local network will that create an island of higher voltage?

Andy B

I was paying attention on the old forum when I was told not to confuse DC with AC and that with AC the current can be pushed into the grid by shifting the frequency rather than upping the voltage.

So will changing the transformer tapping solve the issue or will some dump loads actually be more effective?

Andy B.
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0 Harry Macdonald over 4 years ago

Thanks for this info on G59 and G83.

The inverter is a micro inverter on every panel by Enphase Enlighhten and I am not aware that the settings can be changed - though they might not tell the end user if they are!
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0 Alan Capon over 4 years ago

If you are suggesting that there are several inverters (probably approved to G.83), then that may well be your problem. For 15kW, you need a G.59 system with some proper settings.

Regards,

Alan.
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0 Harry Macdonald over 4 years ago
53 panels and 53 inverters

See: https://enphase.com/en-us/products-and-services/microinverters/family

It also says of this family
"Compliance: AS4777, C10/11, CEI_0-21, EN50438, EN62109-1, EN62109-2, ERDF-NOI-RES_13E_V5, G59/2, G83/2, VDE-0126-1-1 + A1, VDE AR-N 4105"
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0 AJJewsbury over 4 years ago

Ah, just because each inverter individually complies with G83 requirements doesn't mean the overall installation automatically will - especially with that number. IIRC there's a 16A/phase limit on G83 - so you'll be way way beyond that if it's single phase and still likely well over the limit even if it's three phase.

- Andy.
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0 mapj1 over 4 years ago

The fact the individual inverters all meet a product spec, does not mean that a large number of them can be ganged up without problems - it would be worth asking after the original installation paperwork, it may or may not have been done correctly. And as an aside, a large number of inverters may also be an EMC nightmare.
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DNO voltage limits and solar PV generation

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