50kw system advice

[pwboston]

I am asking for some advice on installation of 50kw systems.


I have spoken to SMA tech support and the question I am asking he is unable to answer as they are not AC savvy?

1. We have been asked by our customer to look into installing 2 x 50kw systems on his site. However he has 3 transformers, backed up by HT generators. SMA suggested a G59 relay, but I wanted to confirm that the solar pv would shut down and how? Because the generator is prior to the transformers.

2. What Fit tariff do I use to advise my customer on what he will get. The client will use 100% of his electric generated due to it being a packhouse and coldstore, and at 9p for the FIT + Saving still pays, and the 2 systems would be feeding 2 different MPAn meters, so could they get the 15.2p?

I have contacted DECC and asked but that’s hard work and he couldn’t answer my questions, so I am asking for any advice that people are willing to give.

 

[sedgy34]

fit prices are 10kw up to 50kw =15.2p 50kw upto 250kw=12.9p
you can have this confirmed by his energy suppliers feed in tariff team

 

[pwboston]

because he is having 2 seperate 50 kw systems, albeit on the same site, he could register the first system and get the 15.2p, then when the second is complted register that one and get the 12.9P? and this is assuming he can either get a certificate EPC rating, or exemption, if not then its 9p for it all.

 

[mikefell]

It sounds to me like you wouldnt lose your AC supply with having the backup generators. I would be tempted to try and speak to the DNO to see what their take is on your proposed job. Let me know how you get on, quite interesting this one, I havent come across this problem on any of the large Installs I have done to date.... Regards Mike

 

[pwboston]

Hi, yes this is the problem i am concerned with, although technically he wouldnt send anything back because he is using it, you cant leave it to chance.

The DNO i have spoken to, and because its not their transformer, the customer owns it, again not totally committed to the task.

So im am slightly worried about the advice i need to give and am spending time at the minute contacting people, thats why i was hoping someone would have dealt with this before

 

[JD6400]

I am not so sure it still applies now but i know that in the past (Depending on the proximity of the arrays on a site) even if you were to run in to totally separate mpan's if a further system was to be installed on one site within a calender year of another it would then be classed as one system , so i would make sure this is still not the case .
Just to make it easy we always found that ofgem would only tell you if that was the way they would see it after the commissioning was done !!??
It sounds as if he may already have some G59 relays on his gennys if they are as big as they sound , as for running the solar just with the gennys ( we have never dealt with sma and only used fronius so this may be different for them ) , when talking to one of the fronus uk engineers on a site that he had kindly agreed to help commission two of the first CL36's we had ever used he was quite adamant that the only way to get a inverter this size to run up on a genny would be to (and even then only if you were lucky) use one of them ones that are the size of a tri axle lorry trailer, as anything else would not be able to keep the inverters in toe and they would just set their own limits !

Your best man to speak to concerning whether it would be classed as a single or multi site install would be Ted , if he don't know i can assure you that ofgem will not!

 

[Gavin A]

what size generators and on site consumption are you talking about?

The inverters may trip out instantly at the changeover point between mains and back up, but I'd suspect that what would actually happen is that they'd still be trying to pump into the local grid (generators and on site consumption), which unless we're talking megawatt scale stuff, will almost certainly result in a rapid voltage spike up to the 264V(IIRC) instantaneous cut off point, then the inverters will cut out. Problem is that the rest of the kit on site might not be very happy with seeing spikes upto 260+ volts before cutting out.

I reckon the way to solve this would be via the grid guard code, and changing the instantaneous cut out point to 253V to keep it within the normal operating range of all UK spec electronics kit. You'll need DNO permission for this mind.

 

[pwboston]

I will speak to the DNO further on Monday.

 

[Gavin A]

the other way of course being to connect the Pv system to the grid side of the change over switch for the back up generator circuit.

This would be the best way of doing it if at all possible.