Grid Tied Grief!

[gtuplin]

Ok so lets get off to a good start and say that I am a smart guy and with that the knowledge of the benefits of a good solar installer! I may not ask questions perfectly or may not know all the lingo but I still hope someone can assist in resolving our rather large issue.

To get started I have built and installed a 40kw system that is located on my property in the power transmission company ROW with permits from them as alternative use, it has restrictions from hydro such as being built entirely on wood for safety, fencing to their specs etc. My installer is also following all rules and regulations of the national code so we are 100% above board as he has been doing this for a long time.

Everything is completed as far as install goes, inverters, disconnects, main panel all enclosed in weather cabinets also located under the ROW but for 4 days we are trouble shooting a big issue. The systems seem to only run at about 20% or less so where they should be upward of 9500w each inverter at peak time they are only providing 1200-1500w, turns on late in the am and off late afternoon simply because panel production seems low. The system starts in AM producing about 3000w but declines quick by lunch time . We have tested panels individually volts and amps and find no flaws everything in range and as a point of interest there is the same system running at the house away from the ROW working perfectly. All 4 inverters react the same so kind of eliminates equipment failure and the installer has checked, checked and rechecked everything he and I can think of but can not come up with a good reason why they functions the way they do. This is not the first ROW install as a matter of interest there are many large systems around the world doing a good job in similar locations so what the heck?

The only thing we can think of is perhaps harmonic distortion or interference from above lines but find no reference to such things so here we are asking the questions!

Anyone with ideas I would love to hear from you.



Tech info: Inverters Growatt 10000TL-US

solar panels : Blue Sun 250
4 Strings of 12 panels total 48 (allowable oversize based on location)
Location: Lower Vancouver Island British Columbia Canada
Ambient Temp: day 25c night 18c (summer)

Thanks in advance
Grant

[bcroe]

If you have 48 panels rated 250W, that only comes out to 12KW. Or is that for EACH inverter? Bruce Roe

[solarix]

Can you post the system schematic?

[gtuplin]

[QUOTE=bcroe;n324929]If you have 48 panels rated 250W, that only comes out to 12KW. Or is that for EACH inverter? Bruce Roe[/QUOTE ,

Sorry, yes 48 per invertor total 192.

[gtuplin]

[QUOTE=solarix;n324932]Can you post the system schematic?

That would be something that the electrician would be better at but I can give a description based on what I know.

There are 8 rows of 24 panels, 2 rows per invertor providing 4 strings to each of 4 fused combiner boxes. Each combiner is sent to the inverters and wired to manufactures requirements. Seems pretty straight forward. a lot of grounding as per code and hydro including all modules, all fencing, gates and of coarse all controls, 6 ground rods for fence as well as ground plate for service main AC.
Not sure if that helps at all.

[solarix]

Do your inverters give data on each individual string? They should be very comparable given they are all strings of 12 which should be right in the middle of an inverter's voltage range so doubt that's the problem. What inverter is it? Does the power level fluctuate wildly or does the inverter shut down ever?

[bcroe]

Understand, 40KW requires a corresponding capability at the PoCo. Are you running 3 phase? The assumption here is you have good sun and no shading.

I would first try turning off all but one inverter. If it starts working OK, the 4 of them together may be overwhelming the PoCo facilities.

A test you could run, is open the fuses to half the strings at the combiner box. I wouldn't do that with power running, might cause a big
arc. Next day watch your power numbers. If they are pretty much the same as before, the inverters are limiting and not taking the available
DC. If the power drops to about half, it implies the panels aren't delivering DC power.

Another thing to do is monitor A and V input DC and output AC at the inverter over the day. Note your peak. If DC voltage goes up but
DC amps go down as you lose output (at peak time), the inverters aren't taking the DC power. If the DC voltage is pretty stable while
current drops, its the panels. Bruce Roe

[DanS26]

[QUOTE=gtuplin;n324938]

Can you post the system schematic?

That would be something that the electrician would be better at but I can give a description based on what I know.

There are 8 rows of 24 panels, 2 rows per invertor providing 4 strings to each of 4 fused combiner boxes. Each combiner is sent to the inverters and wired to manufactures requirements. Seems pretty straight forward. a lot of grounding as per code and hydro including all modules, all fencing, gates and of coarse all controls, 6 ground rods for fence as well as ground plate for service main AC.
Not sure if that helps at all.

If all four inverters are indicating the same low output at the same time, then I would look into mis-wiring in the combiner boxes. Electrician mis-wired each combiner box the same way. Only one string is providing power to each inverter.

[gtuplin]

Do your inverters give data on each individual string? They should be very comparable given they are all strings of 12 which should be right in the middle of an inverter's voltage range so doubt that's the problem. What inverter is it? Does the power level fluctuate wildly or does the inverter shut down ever?

No the inverters have 1-4 MMP strings per MPP tracker but appears they combine at the inverter. From the combiners the line is single to inverter then electrician has it divided into 4 to attach to each terminal but at this point they combine as it makes no difference if one or 4 are attached and seems to simply distribute the load.
If you pull fuses from the 4 string combiner box the wattage increases with each string added but very low and about 20% or less. The inverters don't come on as fast as the house system and by 5:30 pm it is shutting down due to poor power supply but when I test modules for voltage and amperage on a single module bases they perform very well and I can not find a bad module in any string.
Inverters are Growatt 10000TL-US

[gtuplin]

[QUOTE=DanS26;n324947]

If all four inverters are indicating the same low output at the same time, then I would look into mis-wiring in the combiner boxes. Electrician mis-wired each combiner box the same way. Only one string is providing power to each inverter.

I agree that the possibility of a duplicated error is present but if it was in the combiner box that by removing string fuses one at a time reduces the available wattage to inverter. Would that disprove that or could there still be a wiring issue in the combiner limiting output?

[DanS26]

[QUOTE=gtuplin;n324952]

I agree that the possibility of a duplicated error is present but if it was in the combiner box that by removing string fuses one at a time reduces the available wattage to inverter. Would that disprove that or could there still be a wiring issue in the combiner limiting output?

If the wiring in the combiner box is OK then double check the string wiring. A clamp on DC ampmeter would be handy here. In other words, are all strings outputing at the same power?

Did the panels come pre wired with M4 connectors or did the electrician need to do any non-standard field connections?

[gtuplin]

[QUOTE=DanS26;n324961]

If the wiring in the combiner box is OK then double check the string wiring. A clamp on DC ampmeter would be handy here. In other words, are all strings outputing at the same power?

Did the panels come pre wired with M4 connectors or did the electrician need to do any non-standard field connections?

All panels were pre wired on the panels and because I have tested each panel individually for voltage and amps with my meter I know they are all wired correctly. So the only add on to the array is the return negative cable to the combiner from the ends of each string and those have been tested for resistance and no flaw found. Now when I tested individual modules the test very good but I did notice that when in the string when connected and he used his clamp on fluke tested the voltage was fine but I thought amps were low which would be consistent with the low watts displayed on the inverter. I get that when I test the module individually it is more of a short circuit test and that in a string I cant see a safe way of performing that same test but I would think amps would be fairly high per string with clamp on test. I don't recall exact readings but it seemed that voltage was consistent to inverter in the 380 range mid day full sun and a reading of maybe 2 amps or less per string, I would think it should be upward of 8 per string but again I am not an electrician and just trouble shooting along side . Would this be an inverter restricting flow for some reason? Perhaps the power is having trouble getting to the grid? Maybe my new 50 KV transformer is bad? I don't know just shooting from the hip!
I seriously appreciate any and all thoughts and ideas, thanks.

[DanS26]

You stated each inverter had four string inputs and that the electrician split the home run down into four connections in the inverter. Are there four fuses in the inverter and have all the fuses been checked for proper operation? Some inverters have plugs instead of fuses.....all plugs there?

Are the inverters programmed correctly?

[sensij]

Please take a picture of how the final wiring is connected at the inverter. If the inverter has several mppt's, but you have just one combined home run, you need to make sure only one mppt is active.

[gtuplin]

[QUOTE=DanS26;n324965]You stated each inverter had four string inputs and that the electrician split the home run down into four connections in the inverter. Are there four fuses in the inverter and have all the fuses been checked for proper operation? Some inverters have plugs instead of fuses.....all plugs there?

Are the inverters programmed correctly?[/QUOTE

Very good questions, I wish I was an electrician!
Ok so I look in the manual and there is no reference to fuses in the inverters but I recall that all 4 terminals are live on the dc side with only one divided wire install so again my assumption is dived to spread load? I am not sure about the plug but I have a spare inverter I will use to check to see if any of the items exist, seems safer.

I have checked manual and there are several options,
(select phase for power balance (opt) )
(set power balance (opt) )
( set grid model) I expect that to be a choice of singe or three phase? I can not see an option to set MPPT option from 1-4 seems default