Can a dirty grid AC sine wave shut down an inverter?

[Shearwater]

Hello Group! I just figured out that my SolarEdge inverter has been shutting down (error 36) and restarting spontaneously for the past 2 weeks. The SolarEdge technician dialed into my system and noticed the grid fed AC sine wave was a bit squared off at the top and bottom and thinks this is causing the shutdowns. Has anyone ever experienced something like this with their system? I have made contact with the utility (SDGE) and hope to get diagnostics from their end soon. Further, the SDGE technician commented that the rise in residential solar back feeds has caused new issues similar to this one in some areas. I live in a newer community and we now have 4 solar installs tied in to our street transformer. Anyone hear of these types of issues? Poor AC grid sine wave seems a little dubious to me!

[foo1bar]

Poor AC grid sine wave seems a little dubious to me!

The inverters are *required* to shutdown when the grid isn't behaving properly.

"properly" may mean over-voltage, under-voltage, frequency isn't in expected range.

It's possible a squarish wave would make it think something is wrong.
It's probably more likely that the inverter is seeing some transient thing that puts it outside of normal operating region for the grid and it shuts itself down. It might be that transient thing is related to or made worse by the waveform you see. ex. it would be fine by itself, but with the imperfect waveform you have it gets it really outside of "normal"

I'd ask nicely that the SDGE guy put a power quality analyzer on your wires.
If he won't and it doesn't clear up in a week or two I'd push harder.
If they still won't after a while, it'd be worthwhile to have an electrician put one on your wires. (After doing some simple checks that all connections are tight, etc)

[inetdog]

The other thing to check on is the grid voltage as seen by the SE inverter.
With several solar installations all feeding power back into the local grid the voltage at the POCO transformer will rise slightly.
And there will be an additional voltage rise along the wiring inside your property and back to the transformer.
If the local line voltage was close to the allowed maximum (well over 120V) with your inverter off it might go too high with the inverter on an minimal load at your house.
But it is likely that the SE would have recorded that overvoltage and the SE tech would have mentioned that.

Did he give any more details about what error 36 is supposed to indicate?

If the scale on the graphs is accurate, the nominal 240V is something less than 220, so low voltage might actually be part of the problem, unless you have three phase 208Y/120, which is unusual for residential.

[Sunking]

Sounds like you might be on a distribution leg with too much solar on it. GT Inverters are very noisy. Get too many too close together and they will pollute the line voltage generating a lot of harmonics and distort the wave form. Additionally if you live in an area with heavy industrial use can also do that by large motor and non linear loads. In CA along the coast AM radio is shredded to pieces from Solar.

[peakbagger]

In most areas the utility has to supply minimum power quality, Nearby large industrial operations can have equipment installed that will impact surrounding properties and occasionally local generation can cause issues. A friend of mine in rural area had issues with poor grid quality. He had to push, but the utility finally did put a power quality analyzer on the line and they identified a couple of local issues. There was a large capacitor bank to support an oil pipeline pumping station that had defective controls and a local hydroelectric station also had lost some controls and the utility was too cheap to fix the, Once these issues were taken care o0 by the utility f, he had no issues with his inverter.

[Shearwater]

Thank you everyone for your insights. The SE fault code 36 is "DC Injection detected on the AC side". I'm hoping that SDGE comes through with a line analyzer next week. I'm also going to talk to a couple neighbors to see if their SE systems are shutting down too. They probably haven't noticed unless they're monitoring geeks like me- so we'd have to look at their SE logs. Lastly, I already have a commitment from my solar rep (Infinity Solar) to do whatever inverter swap out is needed to confirm the issue. My fear is that we find this issue is indeed coming from the grid side and the utility can't or won't do anything about it. These shutdowns are invasive to my production obviously but I'm sure they will shorten the inverter life if the issue is not corrected.

Here's my output from yesterday. Solar generation is represented by the solid green line. You can see the system shutdowns and the the corresponding grid feed (red line) blip up a bit each time.

[FFE]

Wow, you had a load over 20,000 watts for about an hour with a peak of about 23,000 watts. Could whatever that is be part of the issue?

[Shearwater]

Tesla charging! But that happens at midnight so solar is sleeping then.

[FFE]

I was going to guess charging an EV, but it seemed very high.

[cracovian]

Not necessarily closely-related but my Enphase microinverters would should down repeatedly at the peak of their production when putting a heavy load (1.5 kW heaters) on the 120 V circuit (basement and dining room) in my house. Something is wrong with wiring there because I can move heaters elsewhere to burn off solar energy and everything is ok.

[Shearwater]

Not necessarily closely-related but my Enphase microinverters would should down repeatedly at the peak of their production when putting a heavy load (1.5 kW heaters) on the 120 V circuit (basement and dining room) in my house. Something is wrong with wiring there because I can move heaters elsewhere to burn off solar energy and everything is ok.

Thanks for this comment. All of my shut downs have also been at peak production except for one on the above chart from yesterday. I personally believe that is part of the equation and have posed that question to SE tech support- waiting to hear back. I haven't been looking at load so will try to get some data on that to see if there is any correlation.

[Mike90250]

shutdowns at peak production sounds like high resistance from your panels to the power pole transformer. Could be your feed wire, could be your array wires, or even a loose breaker in the panel not gripping the bus bar tightly.

[Shearwater]

My install is new so this very well could be the culprit. I forwarded this info to my solar guy. Thanks!

[bcroe]

shutdowns at peak production sounds like high resistance from your panels to the power pole transformer. Could be your feed wire, could be your array wires, or even a loose breaker in the panel not gripping the bus bar tightly.

The first thing to check for inverter tripping at maximum output, is line voltage. As Mike says, excessive voltage could be caused by too
much impedance in your AC feedlines. Other causes are POCO voltage set too high, or inverter trip point set too low. A combination of
these caused me some grief last year, after a POCO change raised our already high line several volts. Bruce Roe

[Sunking]

Thank you everyone for your insights. The SE fault code 36 is "DC Injection detected on the AC side".

That does not sound like a utility problem. That sounds like you have equipment problems if you are injecting DC on the AC side. I can only assume you have transformerless inverters.

[Shearwater]

Thanks for all the great insight everyone. My solar guy will be on site on Monday to make sure all the connections are tight- particularly on the AC side. Next, I will keep the work order open with SDGE to see if they can come out and put a line analyzer on my grid feed to check for anomalies from that end. Last, I'll want to keep the ticket open with SolarEdge so that I/we can really understand the nature of these shutdowns. I'll keep you all informed on whatever progress I make. Cheers!

[Shearwater]

Closing the loop on this topic. SDGE was kind enough to put a data capture device on my electrical panel for about a week. Afterwards, one of the engineers contacted me to discuss the results. On the grid side, everything was more/less normal. The only anomaly they saw was a fairly decent voltage drop when my Tesla charger engaged at night. They suggested lowering the charge setting to a lower amperage if I don't need such a quick charge (currently charging at 80 amps). But while all of that was happening, my inverter had almost completely died on its own- throwing out at least 4 different fault codes daily along the way. When I first reported this issue, the inverter would only shut down after reaching max power. By the end of the week, it was shutting down and restarting every few minutes. Thankfully, SolarEdge drop-shipped a new inverter right away and my solar guy (Infinity Solar, Orange CA) popped it in and I was back in business. Good experience working with SDGE and Infinity Solar. Everyone was helpful and the issue was resolved with minimum impact. Thanks group for your input as well!