Solar Panel Output cutting out

[Motters]

Hi

I had a solar panel system fitted 22 Feb 2012. The system includes a 15 panel sharp 245 array split into 2 strings of 9 and 6 running into a Sunny Boy 4000TL.

They system seems to produce consistently until about midday then cut out for periods if there is a decent amount of sunlight. I have been monitoring the system with Sunny Boy Explorer and noticed if the combined string voltages exceed 500v then the output drops to 0A and 0W. This remains the case until the voltage drops below 500v.
When running normally the volatges for each string are 280-290V and 170-180V. This can then jump to over 300V and 200V and knock the system out. I believe the inverter operates up to 550V. Would changing the inverter to the 4000TL with Reactive Power Control which has a 750V limit cure the problem or is there a more fundamental issue here.
I have also noticed recently that output power has sometimes been exceeding 4.2KWh which seems strange for a system with a stated output of 3.675KWh.
The installers have been around a couple of times and seem a little mystified but have suggested replacing the inverter as a first solution.
If anyone can offer me some advice I would be most grateful.
Cheers
Motters

 

[SolarCity]

Do you get any error messages on the inverter when it cuts out?

 

[Motters]

Hi
The only fault I have seen is on the software as Grid Fault(1) and this seems to switch from an incoming fault to an output fault.
Thanks for your reply.
Cheers
Motters

 

[SolarCity]

I don't see the setup as being a problem. Looks fine to me with those voltages.

Grid fault does sound more likely to be the problem.

Is your installation in a rural area? Is your install far away from the electricity meters?

I supect that you are having issues with high voltages - caused by high grid voltage or voltage drop. Or it could be that your inverter isn't set up to G83 - although that seems unlikely if your installers have already been out twice already.

 

[Motters]

Hi
Thanks for your reply. Yes I am in a rural area and the run from the inverter to the meter is about 10m.
Voltage in this area is about 242v nominally.
Is there a reason why the system is fine up until about midday ??
Is there a realistic solution to this problem, will changing the inverter sort it out ?
Not an electrician by ant standards, my understanding goes about as far as A level physics and that was quite a few years ago. LOL.
Thanks again for your reply.
Cheers

Motters

 

[SolarCity]

The grid voltage can sometimes peak around midday so this tends to be the time when it would kick out - particularly if there are other installs in the area that are exacerbating the problem.

10m should be fine for the cable run to the inverter, as long as the cable size is big enough - should be at least 4mm2, possibly as much as 6mm.

From the info you have given, I'd be surprised if the problem was the inverter and therefore changing it, in my opinion, would not help solve the problem.

 

[FB.]

The grid voltage can sometimes peak around midday so this tends to be the time when it would kick out - particularly if there are other installs in the area that are exacerbating the problem.

Yes, grid voltage in my neighbourhood was typically 238-242V, but now that sunnier weather is here (and there has been a bit of an outbreak of PV locally), the grid voltage often runs at 245-250 on sunny days.

 

[Motters]

Hi
Thanks again for your replies. Is there a solution to this or do I just have to live with it?
I wondered if FB had had any problems similar to mine as the voltage in that area seems similar.
Thanks again
Cheers
Motters

 

[FB.]

Hi
Thanks again for your replies. Is there a solution to this or do I just have to live with it?
I wondered if FB had had any problems similar to mine as the voltage in that area seems similar.
Thanks again
Cheers
Motters

No problems at all with my system.
I work from home so if I'd be more likely to notice a problem than most people.
I have an Aurora PVI-3600-UK and the manual says that it operates at grid voltages in the 211 to 264V range.

 

[FB.]

Does the grid fault error message coincide with the power drops, or is it just at dawn and dusk? My inverter sometimes flashes its error lights briefly at startup and shutdown.

I didn't notice you mention whether you panels have anything at all possibly shading them around the time of their power drops. This is well-known and has been a much-discussed issue on here.

 

[sedgy34]

ive looked on sunny design and a 4000tl20 is fine to have with your system
sma technical helpline is the best people to ask as they made it 01908 487569 or 01908 304850

 

[sedgy34]

im assuming you have a TT earthing arrangement the ac cable installed cannot exceed 1ohm as sma state. this could be the problem

 

[Motters]

Hi
No shading issues and its difficult to be absolutely sure if the faults occur at the exact moment it cuts out.
The inverter Output Voltage range is 180-280V AC and can be adjusted to suit different countries. How does this affected or cause the input voltage to jump to over 500V.
Getting a bit out of my depth here.
Cheers
Motters

 

[Motters]

Hi Sedgy thanks for your reply. Cable is 4mm so I have been advised is suitable for the job. Not sure about the earthin.
Thanks Motters

 

[SolarCity]

Hi
No shading issues and its difficult to be absolutely sure if the faults occur at the exact moment it cuts out.
The inverter Output Voltage range is 180-280V AC and can be adjusted to suit different countries. How does this affected or cause the input voltage to jump to over 500V.
Getting a bit out of my depth here.
Cheers
Motters

The input voltage that you are talking about is the DC side of the inverter - this voltage does not affect the voltage on the AC side.

High impedance could be the problem and this may mean that you'd need to install a different model of inverter.

What has your electrician said about it? Has he ruled out any of the possible issues that we have suggested?

 

[Earthstore]

Could this be the same problem that sanyo/SMA had?
If the system is split on two strings, is it possible that just as the sun is coming around the inverter is searching the wrong power curve, maybe switching the optitrac on would cure it?
Just a thought.

 

[GaryM]

Cable is 4mm so I have been advised is suitable for the job.

Don't SMA recommend 6mm2 for the AC cable and not 4mm2 as the OP states he has?

 

[SolarCity]

I don't think this is a Sanyo/SMA compatibility issue as there are grid fault error messages. I would also doubt that the cable size is the issue.

 

[Earthstore]

Another suggestion then, put 2x24hr voltage monitors one on the incoming and one at the inverter, this will then show you what it is really happening and give you some accurate data to work with.
I am aware that the DNO have such a system, not sure where you can obtain them from though.
In my opinion it is normally an installation/design problem rather than the grid, but never say never.
Just another thought.

 

[Glen Powell]

I have found if more than one install is on the same line the the wire size does matter, I do not know the reason why this is, however we had an install of 2 x 3kw systems ground mount 15meters away from house, both properties were tripping, one was on other was off scenario. we changed the wire from 4mm to 10mm after DNO said no problems on grid.

After changing the wire both systems have worked perfectly well, the 10mm was a bit overkill but I do beleive there is a fundimental problem with feedback to inverters in close proximity, however that would not really explain how changing the wire size would help.