Grid Tied Grief!

[solarix]

I get the feeling this is an inverter problem. The fact that all four of them are acting the same rules out a product failure, but they are definitely not acting properly and you should get the manufacturer's techline involved except it doesn't appear to have one. Try calling their main phone 800.374.4494. Grosolar is not a very common brand and not having a tech service is a major dis-qualifier in my book.

I don't think the grid can refuse the power like this. If there was enough line impedance to restrict the power, the voltage would go up enough to trip the inverters off - not throttle them to partial power. Interference from overhead powerlines? That's grasping at straws.

The 50kV transformer could somehow be the problem. Why is it even there? Are you feeding a high-voltage line? Is it possible to remove the transformer and just run one inverter into the grid?

I've never seen an inverter throttle back due to an AC side issue. I would think the only way to have them running at a low level is if the array power level is low.
All very interesting.

[DanS26]

I wonder if those inverters have some type of throttling device or program based on say a heat sensor or power supplied. The output power curve would indicate throttling. Since they all operate the same, that would indicate a factory default setting.

[gtuplin]

[QUOTE=solarix;n325028]I get the feeling this is an inverter problem. The fact that all four of them are acting the same rules out a product failure, but they are definitely not acting properly and you should get the manufacturer's techline involved except it doesn't appear to have one. Try calling their main phone 800.374.4494. Grosolar is not a very common brand and not having a tech service is a major dis-qualifier in my book.

I don't think the grid can refuse the power like this. If there was enough line impedance to restrict the power, the voltage would go up enough to trip the inverters off - not throttle them to partial power. Interference from overhead powerlines? That's grasping at straws.

The 50kV transformer could somehow be the problem. Why is it even there? Are you feeding a high-voltage line? Is it possible to remove the transformer and just run one inverter into the grid?

I've never seen an inverter throttle back due to an AC side issue. I would think the only way to have them running at a low level is if the array power level is low.
All very interesting

Oh I understand the idea of product problem or failure and is it possible to have a volume disaster? I would have to say of coarse it is if manufacture had a bad run. But I tend to rule that out as there are two identical inverters and solar arrays all same same running perfectly! I suppose I could try moving the spare inverter into the system to see if it changes anything. I would also have to consider the fact that out of 7 inverters 6 in service the manufacturing dates all very by months so if this was the case I would expect a massive out cry given the numbers out there based on serial numbers.
Based on this however I could contact support and see if they have anything that could assist.
The transformer was installed when hydro installed a new pole to access the solar system, I have a power line that comes off the street grid runs about 800 feet to my last pole which has a 25KV transformer then it goes to the meter base from there. The new line is pulled off the 800 foot run at one of the poles on the property and runs 130 feet to new pole which has meter base on it then a short massive underground line to the main AC disconnect at the solar system, the 50 KV transformer was installed on the original pole where the new line is drawn from. I don't know a lot about transformers but this is a good sized unit! Its just good old regular single phase 240 volt.
I do feel better that you don't suspect the ROW high power overheads.

[gtuplin]

I wonder if those inverters have some type of throttling device or program based on say a heat sensor or power supplied. The output power curve would indicate throttling. Since they all operate the same, that would indicate a factory default setting.

I get the idea of it and maybe a good idea based on some scenarios but why would it limit power at early start up to the point of coming on hours after the system away from the set of four as well as crap out at the end of the day 3-4 hours prior to the isolated one? This whatever it is seems isolated only to the group of four!
I have many extra panels, perhaps I will set up a string of 10 along the fence away from the field and test the spare inverter for theory and if it is fine pull an inverter from the field and test it to see if anything changes! Man I don't know, this is really crazy stuff for me, one week of trouble shooting sucks and running out of ideas.

[gtuplin]

All I have left is grasping at straws now so here is a question!
The system is all new, we are trouble shooting and testing system and once all is well we submit final inspection and or contractor approval to the net metering division of hydro a contract is made and they then start to collect data from my smart meter. Is it in any way possible that because the meter is not perhaps synchronized or what ever by hydro that it could limit line access? It does measure what outflow there is but the account really is not set up until paper work is complete, what ever is sent out is a gift but we are just testing.

[SunEagle]

It looks like black and red wires are being combined in the combiner. Am I seeing the picture correctly?

I see the same thing which leads to my question about there being some type of wiring issue between the panel strings and the inverter. I would like to see an over all wiring one line of the system but even that may not help with trouble shooting the issue if the field wiring does not follow the drawing or if there is a component problem.

I have performed enough of these root cause findings in my life to know that without being there or having someone that knows what to do (I am not criticizing the OP) doing it through a forum will end up following a lot of false leads down rabbit holes.

[solarix]

I'm not saying the inverters have failed, more like there is something about the way they operate that is not understood. Like I had an instance where the input voltage on the older SMA 4000s was especially narrow and would not work when firing it up in the middle of a hot day cause the array voltage was too low. There is something here not understood which is why I suggest calling the manufacturer. Seems like they must have some kind of throttling feature. These things always occur on a weekend right?

The revenue meter can't limit your power flow, but it could credit it wrong until the right one is installed.

[jflorey2]

So back to my original question, does anyone think that the high power overhead transmission lines could be causing some interference in some way . . .

Possible but unlikely. (I assume your array frame is grounded.)

or how about my new 50kv transformer could it be malfunctioning? can that even happen? Can the grid refuse power?

Not really - other than by going up too far in voltage, which is something you can check with a meter.

Other things I would suggest -
String by string test of current (with inductive probe) and voltage (with meter.) If one is wildly out of whack there's your problem. If, during operation, output voltage is close to Voc but output current is low, it's the MPPT in the inverter.

Power quality monitoring. You can do this manually with a meter (make sure you get one that measures frequency as well) but getting/renting a dedicated monitor would be a lot easier/more effective.

[gtuplin]

I am down taking data and wanted to point out that today is cool and partly cloudy and inverters are putting out about 20% higher compared to same time yesterday full sun warmer.
Just first major change to note.

[J.P.M.]

I am down taking data and wanted to point out that today is cool and partly cloudy and inverters are putting out about 20% higher compared to same time yesterday full sun warmer.
Just first major change to note.

If it's partly cloudy, the lower input has a lot to do with the lower output, but the lower temps brought on by lower irradiance would needed to boost output by 20% would mean about a 40 deg. C. lower panel temp. That's not likely.

[jflorey2]

I am down taking data and wanted to point out that today is cool and partly cloudy and inverters are putting out about 20% higher compared to same time yesterday full sun warmer. Just first major change to note.

That's a pretty strong indication that panel temperature is a likely culprit - and that your system may be on the hairy edge of minimum voltage. The data sheet lists your minimum voltage as 345 volts; are you sure your Vmp is well above that at your expected operating temperature? (Your operating temperature is generally 20C or so above the STC numbers on your panel's data sheet, which means lower voltage during operation.)

From estimates based on your description:
Panel Vmp = 30.4 volts
Vmp at 25C: 364.8

Vmp after 2% wiring loss: 357 V
Vmp after 20C rise: 330V

I'd check voltages. If your inverter will really not operate well outside its rated voltage range, your system may be limiting due to a too-low voltage at the inverter input.

[J.P.M.]

I just went through this thread again and note that there is no mention of array orientation(s) (tilt & azimuth), any shading or estimates of performance. OP: Since we're all throwing darts, any chance things have some weird set of orientations ? Also, were you given, or did you do anything in the way of performance estimates ? Also, any way to estimate insolation levels during all this underperformance ?

Maybe I'm stupid, or going blind, or both, but I seem to be missing some basic information here. Knowing array orientations would allow a dart throw estimate of clear day performance. That might be helpful in the analysis. Not meant as an insult, but do you know that array orientation (tilt & azimuth) and shading has a bearing on performance ? Or that system output is variable ?

[sunnyguy]

So individual panels produce expected voltage and current but strings produce expected voltage and significantly reduced current? What jflorey2 says could be correct if string voltage is too low for inverter, outside mppt range. But that doesn't make sense if the house system is also same panels and string length.

[gtuplin]

So individual panels produce expected voltage and current but strings produce expected voltage and significantly reduced current? What jflorey2 says could be correct if string voltage is too low for inverter, outside mppt range. But that doesn't make sense if the house system is also same panels and string length.

According to the inverter the voltage seems good at 385-390 and you are correct that the house system is fine.

[gtuplin]

[QUOTE=J.P.M.;n325063]I just went through this thread again and note that there is no mention of array orientation(s) (tilt & azimuth), any shading or estimates of performance. OP: Since we're all throwing darts, any chance things have some weird set of orientations ? Also, were you given, or did you do anything in the way of performance estimates ? Also, any way to estimate insolation levels during all this underperformance ?

Maybe I'm stupid, or going blind, or both, but I seem to be missing some basic information here. Knowing array orientations would allow a dart throw estimate of clear day performance. That might be helpful in the analysis. Not meant as an insult, but do you know that array orientation (tilt & azimuth) and shading has a bearing on performance ? Or that system output is variable ?

Good call, you are right I never provided that info.
The entire array is situated almost perfect due south and the angle was set at 44 degrees as a permanent angle and was calculated for best February to October outputs based on our location. The winter was not a concern as it is primarily light rain cloud and short days. There is a slight shade now in the early morning but only effects a few panels then clear until sun down.
I can only compare this system to the running system and it is pretty much the same orientation.