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DNO Witnessing commissioning of a G59/2 Installation 50kW

Discuss DNO Witnessing commissioning of a G59/2 Installation 50kW in the Solar PV Forum area at ElectriciansForums.net

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Regular EF Member
Just about to Install a 50kW system. The DNO have asked to witness the commissioning of the system.

Can someone give me an idea of what they would expect on the day?


Electrician's Arms
If you have applied under G59/2 expect them to check the warning stickers are in the right place and check the system shuts down when the power is cut. All in all not much for £750!



EF Member
The DNO can ask you to carry out any test they wish for instance.

Under and over Frequency
Under and over voltage
Loss of mains
Vector shift

If you have not carried out any testing previously or you do not have the test equipment, I would recommend getting a consultant to carry out the testing for you. Hope this helps


Solar Guru
Can strongly recommend SolarTest for on-site commissioning assistance, they're very well known by all the DNOs and senior assessors around the country. Most 3rd party testing houses charge around £500 for on-site commissioning and take around 4hrs on average apparently. The test equipment itself can cost around £11K to buy if you were to do it yourselves. I'm not 100% au fait with the exact nature of the tests but I'm sure Princesolar has it pretty much covered in his post above.


Forum Mentor
It is not something you can do yourself without that very expensive test kit !
We used to use a company from the reading area for the G59 relays and testing when needed , their blokes were mostly South Africans and were worth the money just for the stories of home, alone !!!
Who's your DNO , as we found that if you could provide proof of G59/2 compliance for the inverters then that was enough to keep them at bay ?


I can recommend a company called DEIF (UK). They're a large company that specialise in power geneation controls and have a G59/2 protection relay in there product range. They also sell a "ready built" G59/2 Protection Panel that you can install easily in many locations. They have experienced test engineers that will perform a witness test anywhere in the UK and as they produce the relays, they have great product knowledge. Have a look at www.deif.com.
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