3 phase solar PV installation

[Axolve]

Hi

This is my first post so I hope I am getting it right.

I have been asked to install a 10kWp system in a paddock next to a house and close to major overhead pylons. The DNO is upgrading the supply to 3 phase and I will install 3.3kWp on each phase under G83. I have 3 questions.

1. As the house will be supplied with electricity from one phase, I assume the owners will only get the benefit of the electricity generated from the 3.3kWp system on the same phase. Is this correct and if so, to benefit from all of the electricity generated, will they need to have 3 phase in the house with different parts of the house on each phase?

2. Does anybody know of a good supplier of stand alone mounting frames to put in a field with sufficient space beneath for sheep to keep the grass down?

3. Will the overhead pylons (not sure whether 440 kV) have any impact on the solar modules or inverters installed on the ground directly below the pylons?

Thanks

 

[PV Martin]

Hi Axolve

I have recently installed a similar system, but mine was an off grid system where i created a grid from a genset/battery/inverter arrangement.

1. In answer to your questions (and what i done) is that you can common up the inverter's within a junction box or an isolator taking the system down to a single phase, the 3 inverter's will syncronise with each other and the grid. it is an expensive solution as you need to buy 3 inverter's but will allow a G83 connection. that way the owner gets full benefit from their system.

2. the Schuco ground mount systems are pretty good, but it sometimes works out cheaper to have something fabricated yourself, you then get exactly what you/the customer wants.

3. i cannot answer this one sorry.

Hope this helps?

 

[Worcester]

@Axolve Schletter do a good ground mount system, if you make something yourself you'll need to hvae it designed by a structural engineer and give appropriate warranties, also Wind And Sun have a cost effective british made product.

 

[Axolve]

Hi PV Martin

Thank you for your advice. The DNO require me to feed 3.68kWp into each phase rather than combine the lot into a single phase. I will look at the Schucco ground frames.

Hi Worcester

Thank you for the advice on the Schletter and Wind and Sun frames. I will look into.

 

[VMan]

I have a similar question, we have been asked to price a system of 9.8kwp, but when we arrived the lady wanted us to price for as much as possible

She has 2 x 3 phase supplies with electronic meter on each 3 phase supply which records the individual phases.

Do you think it would be easier to put a 4kWp on each phase and go for G83 or go for G59? i havent looked into G59 at all yet so not sure what it involves.

Thanks

 

[Worcester]

@VMan,

TedM kindely berated the ENA earlier this year, thanks to him for this:

To ENA:
f) can you confirm the maximum Watts applicable to a 3-phase supply?

Answer:
f) 230x3x16= 11,040 for practicable purposes this is 11kW, split evenly over three phases. The following is not allowed
phase 1 4kW
phase 2 4kW
phase 3 3kW
as two phases exceed 16A per phase

Unbalance is allowable up to to the following limit
phase 1 3.7kW
phase 2 3.7kW
phase 3 any value under 3.7kW

 

[VMan]

Thanks, i will contact the DNO to discuss on Monday i think as she has 2 3 phase supplys. i wonder if i could put 3.7kwp x 6??
i was looking at the sunnyboy tripower someone suggested to me yesterday, this way i believe it will keep me on G83-1.

 

[solarfred]

Hi PV Martin

Thank you for your advice. The DNO require me to feed 3.68kWp into each phase rather than combine the lot into a single phase. I will look at the Schucco ground frames.

Hi Worcester

Thank you for the advice on the Schletter and Wind and Sun frames. I will look into.

I just finished erecting a Shuco Ground mount for 10 kw so please let me know if you are going this route. We used ground anchors instead of tons of concrete so this takes a couple of hours to complete and everything can be laser levelled. I had fabrications made up for the Schuco feet to bolt onto the ground anchors so all the fixings could be plumbed using a neat bit of kit from the anchor company.
The kit ground mount is a little over engineered and the instructions are pants. I have parts I do not need and do not have parts that I did need.The parts were on the order form but not on the truck. Shuco failed in many aspects. Oh and do not bother asking for the end caps for the horizontal rails (as proudly shown off at Ecobuild - as they do not exist!!) They were dummies - and I felt like one when I asked for a set to make the ends of the rails kind to human flesh. We will have to make something up ourselves which for a £5,000 bit of kit is a little irritating.
Maybe they should stick to window frames.

 

[JD6400]

VMan if you do go for 6x 3.67 kw , you would be looking at least g83/2 .
Maybe G59 , dependent on who your dno is as this will be one generation site .
And you will be on the the third rate tariff as well .

 

[JD6400]

Hi Axolve

I have recently installed a similar system, but mine was an off grid system where i created a grid from a genset/battery/inverter arrangement.

1. In answer to your questions (and what i done) is that you can common up the inverter's within a junction box or an isolator taking the system down to a single phase, the 3 inverter's will syncronise with each other and the grid. it is an expensive solution as you need to buy 3 inverter's but will allow a G83 connection. that way the owner gets full benefit from their system.

2. the Schuco ground mount systems are pretty good, but it sometimes works out cheaper to have something fabricated yourself, you then get exactly what you/the customer wants.

3. i cannot answer this one sorry.

Hope this helps?

Hi PV Martin
If you do combined all three to get to 10 kw on a single phase connection you definitely run the risk of having to go G59 , all of the system planners that i have spoken to say that this is by far their most disliked connection due to the potential of unbalancing of their lv supply side .

 

[PV Martin]

Hi dpelectricalltd,

i hear what you are saying, and on a grid connect there are more hoops to go through, but my system was off grid so a little more freedom, although many more headaches as we had to create the grid in the first place.

 

[JD6400]

Hi Martin

I did see that it was off grid and was suitably impressed , to be honest we have been approached several times for one of these and so far declined ( last week was the latest one ! ) .
I am sure that we are not only the company / people , that would really appreciate learning how you would even start to go about such a project !
Maybe one day if you find time you could start anew thread and share some of your experiences , i am sure it would have huge following !
P.S if you do get around to doing so please do pm me with it as i am sometimes away from the net for 3-4 days at a time and would be disappointed to miss it .
Many Thanks

Dave