G83/2 question - 50kW PV installation

[Ivan]

Does the DNO have to witness switch-on for a 50kW installation under G83/2. I'm working on a couple of projects where the DNO engineer has been quite helpful and has volunteered his services to witness switch-on (at considerable cost) - is this necessary, or at DNO's discretion, or is this optional from my point of view?

[guydewdney]

dont you mean G59?

[GavinA]

Does the DNO have to witness switch-on for a 50kW installation under G83/2. I'm working on a couple of projects where the DNO engineer has been quite helpful and has volunteered his services to witness switch-on (at considerable cost) - is this necessary, or at DNO's discretion, or is this optional from my point of view?

discretionary, type tested kit should be acceptable. If none type tested and you've no experience testing the protection settings then getting an expert such as the guys from G59 testing.co.uk (erm I think) to do the testing for you could be more cost effective and the DNO should accept that without needing to witness it, unless you're really confident in what you're testing for.

On the other hand, having a friendly dno engineer might be worth the cost in the long run.

[Ivan]

Guy, there is a concession for installations above 16A per phase but under 74A (ie 50kW into 3phase) where you are allowed to certify under G83 with a few minor changes to the settings of the inverters.

Gavin, The installation is 3 x SunnyBoy Tripower 17000s which have g59 certificate (for what it's worth). Does it therefore need testing of any sort? If these are G59, do they still need their settings altered? What would you suggest?

[GavinA]

Just tell them they're type tested to G59 protection settings SMA inverters, and you have no intention of conducting further tests of the protection settings so there's nothing to be witnessed beyond the standard ac and dc insulation resistance tests etc.

slight fly in the ointment would be if they actually wanted you to use the G83 settings with just one part adjusted, as has been the case with some G83/1/2 applications. I'm not entirely clear whether this would require a new test certificate for the new settings, or if it would be covered under the original type test cert, but as it was agreed to be done as a stop gap measure to ease the process, I can't see the logic in requiring a seperate test.

I do think the witnessing is a discretionary thing still though, so the DNO could probably insist on it, but I'm not 100% on this - I think it's in either the G59 guidance or possibly the more detailed version in a table, and it varies with the system's size. type tested g59 inverters weren't an option for what I was looking at when we went through this, so I'm not 100% sure what the situation is. Not really my speciality tbh.

[Other-Power]

In my experience, G83 stage 2 means log in with grid gaurd and change over frequency to 51.5 Hz.  Commision the install and tell your DNO what you have done.

G59 is a lot more work your DNO could/probably will ask for a representative to come and check the settings and this costs a lot, I would push to connect under G83 stage 2.

Cheers

Jon