DNO over frequency requirements

[edexlab]

We've received a note from WPD with an application which has been approved in South Wales which is out of our usual area although same DNO different office:

''As a temporary measure(until 2nd March 2012) G83/1-1 may be applied to inverter connected generators rated between 16A per phase and 17kw per phase (ie 17kw for a single phase device,34 kw for a split phase device and 50 kw for a 3 phase device) as long as all of the following criteria are satisfied:

• The G83/1-1 stage 2 process is followed
• The Generator is connected through an inverter that is type tested to G83/1-1
• The over frequency protection setting is set at 51.5Hz with a time delay of no more than 0.5s . Note a setting below or above 51.5 Hz is not acceptable. All other protection settings shall comply with the Requirements G83/1-1

New setting is confirmed as part of the Commissioning confirmation.''

The third point is the one I'm concerned about ,having looked at the G83/G59 certs for SMA inverters which we use the most the over frequency setting is

G83 50.5 Hz +/-0.5 % at <5 seconds
G59 limit 51.5Hz <90s 52Hz <0.5s

These new figures are between the two

Can I change this using Sunny Explorer (with Grid guard code)? I have to admit I've not had to make any changes to the settings (other than the passwords) before although I'm sure I've seen it on the adjustable parameters
any advice would be appreciated

As for confirming the new setting is this a case of just adding a note to the commissioning form stating that its been changed or is a printout likely to be required?


And out of curiosity anyone know why they would do this as a temporary measure ,will this mean that they may revert to original settings at a later date ,and will we have to alter already installed systems later on?
I have sent these questions to the DNO and await their reply

 

[SolarCity]

Yes, you can change the settings via Grid Guard code simply enough.

And as for the 'temporary measure', I suspect what they mean is that they are temporarily relaxing the rules and that NEW installs after 2nd March will revert back to pre-notification.

This is interesting. Which WPD area is this?

 

[edexlab]

I have spoken to the engineer and he does'nt know why its being altered for the meantime , all installs over 16A to be applied for as per usual, but with this new setting
after March 2012 all jobs >16A in the uk will go under G59 and require the correct certification or relay fitted
Interestingly he said that most inverters will probably need a relay anyway regardless of having a G59 certificate as they cannot have an injection test carried out by the DNO, I said if its been type tested then surely this is wrong as this was the whole point of gaining the test certification, he then went on to say that either Fronius or SMA's G59 certificated inverters would not be accepted at present as there were errors on the certificate and advised me to check.
He seemed very knowledgeable and I'm inclined to believe the majority of the above to be true
He also said this is a national directive for all DNOs to comply with.
this engineer is based at the Swansea office.

 

[Worcester]

@edexlab

Working with the same DNO (WPD) different office, they are more than happy with the SMA's and on a recent install have cancelled their inspection / injection test....

Now of course that all may change in April 2012, however I doubt it.

I believe G83 is also being updated.

What doesn't make sense is that just because it doesn't have a relay, doesn't stop you doing or monitoring an injection test.

 

[edexlab]

I agree, the Dno engineer presumably brings this tester on site connects to circuit, inverter switches off within prescribed parameters ,everyone's happy.

I've not been down the G59 route yet the largest job we've done so far was a 27 kw which they accepted under G83 as it was a 10 and 17 kw on the same site but differing metered supplies on the same branch

I have already sent the SMA G59 certs to WPDs technical office (Bristol) as he recommended for them to inspect, to which they are supposed to let me know if they are correct, this I think is probably pointless as I'd be amazed if they had'nt already checked them out.
Other points I made were G59 applications I have'nt as yet done one but I had a look sometime ago and it did look complex as I remember ,I asked whether there may be a simplified version made available
he agreed it would be a good idea as the majority of installers would struggle and they themselves would not be able to cope with the paperwork load
and also it would make sense if there are issues with some manufacturers certification then why can't the Dno list the compliant ones on their website He replied that its not up to the DNO to do this ,fair enough but it could save everyone a lot of time including themselves
some things are just too simple!

 

[Worcester]

Yep though you have to provide the testing equipment and injection gear, it is just a 'witness test' so there are quite a bit of extra costs.

If they won't be able to cope with the paperwork, they won't be able to cope with the witness testing workload either - and by the way a witness test is charged at £350 + vat and you'll need to add at least half a day of your time into the job as well ... assuming they turn up on time ...

If they have issues with some suppliers certifications, what's the point of the certification?