Solaredge ground fault isolation fault

[foo1bar]

Now... what to do?

If it were me, I'd junk the one that has a short.
And see if removing that got things back working.

I'd probably test each of the other 11 and write down what the test results were so I could check them the next time I had cloudy/rainy weather and was having problems.

Since it was working most of the time, just giving a fault on cloudy/rainy days, I think there's a good chance it'll work fine once the panel with the short is removed.

[qrper]

I'm not much of a car guy. However the friends that I know that tinder with cars have always told me you need the right tool for the job.

How true!

The Klein megger showed up a bit earlier than UPS normal deliveries.

It was getting late, but the results, while not eye openers, sure confirmed what I had thought to be the problem.

The used modules are not worth a crap in this grid tie installation.

According to Solaredge, a good module should be at least 80MΩ when both leads are shorted together and measured to the frame.

To set a baseline, I tested one of the new Hyundai panels and it should 4000MΩ

I tested one of the used Trina panels and it showed 1.8MΩ

One panel would not test because the meter detected voltage to ground. That was the panel that I read 27 Vdc with the Fluke to ground. I never did break out the Simpson 260.
I checked random panels out of the 12 and some were in the 100MΩ to 1200MΩ.

Then there were the ones that showed 2MΩ, 30MΩ, and 40MΩ.

Clearly these panels won't be able to be used in a grid tie installation. I wonder if that is why they were pulled to begin with?

Bottom line, without that Megger meter, I'd still be chasing my tail.

Now... what to do?

I'm mike

[bcroe]

My own measurements on a pair of 2 year arrays each showed some 100 megohms to ground,
at 450 VDC including 56 panels in sun, 460 feet of 6 gauge wire in plastic conduit, and all the
PV wire connecting the panels to a combiner box. This in Feb. The leakage may not be linear
with applied voltage, which is why I would not use a simple ohm meter. Bruce Roe

[qrper]

You could start taking things apart, but do not leave MC4s hanging in the weather. It will not take
very long for the contacts to start corroding. I made up a bunch of dummy plugs for protection,
with the wire hole sealed and the clips ground off. Bruce Roe

Most likely UPS won't be here until 4-5 pm, and then It's suppose to rain. That's a good idea about using MC4 connectors as plugs. However, I'm going to leave all the wiring intact until the meter/weather corporates a bit.

BTW.. disconnected the used panels sub-array and the isolation value as reported by the Solaredge inverter is now 11,000k Ω. With the used panels, this morning it was 593KΩ. According to Solaredge, anything under 600KΩ will fault the inverter. The other day, I checked and isolation value was 600.11kΩ and the inverter was still producing power.

[bcroe]

My Megger should be here today, if UPS shows up early, they don't usually make
it here until later in the afternoon, and with snow and rain forecasted for this afternoon, may not get
much done.

You could start taking things apart, but do not leave MC4s hanging in the weather. It will not take
very long for the contacts to start corroding. I made up a bunch of dummy plugs for protection,
with the wire hole sealed and the clips ground off. Bruce Roe

[qrper]

I had an isolation fault on my SolarEdge array last year. As you have realized, it is not necessarily the same as a ground fault.
The issue I had was that one of the conduit connections had come loose and the entire vertical section of conduit filled with water and froze. The ice caused enough damage to the insulation of one of the wires to generate the isolation fault. Not enough to cause any ground fault, just enough to partially compromise it's integrity. As soon as the ice melted I pulled new wires and it worked fine again.

I would check all of you wires and make sure they are properly rated for wet conditions, and you don't see any damage. Also check all connections to make sure they are water tight.

That about sums the issue up. Like you said, it's not a ground fault, but an isolation fault.

I've triple checked all the connections, every MC4 was popped open and inspected. Because this is a ground mounted array, none of the wires are in conduit. However that being said, the wires are PV rated 1000Vdc direct burial and so on.

My Megger should be here today, if UPS shows up early, they don't usually make it here until later in the afternoon, and with snow and rain forecasted for this afternoon, may not get much done.
I still suspect those used panels I have on half the array.

[emartin00]

I had an isolation fault on my SolarEdge array last year. As you have realized, it is not necessarily the same as a ground fault.
The issue I had was that one of the conduit connections had come loose and the entire vertical section of conduit filled with water and froze. The ice caused enough damage to the insulation of one of the wires to generate the isolation fault. Not enough to cause any ground fault, just enough to partially compromise it's integrity. As soon as the ice melted I pulled new wires and it worked fine again.

I would check all of you wires and make sure they are properly rated for wet conditions, and you don't see any damage. Also check all connections to make sure they are water tight.

[qrper]

Be VERY careful with a megger. They often use high voltage to test for leakage, and most panels are only rated to 600V. You risk damage to panels if you test above the panel rating. Some +250V panels now come with a 1,000v rating, but know what your test gear is putting onto the panels.

Will be! The test will use 500 V dc. According to SolarEdge, the two leads from the panel are shorted together and then they connect to the positive side of the megger. The negative side goes to the frame or array mounting structure. screenshot_226.png

[Mike90250]

Be VERY careful with a megger. They often use high voltage to test for leakage, and most panels are only rated to 600V. You risk damage to panels if you test above the panel rating. Some +250V panels now come with a 1,000v rating, but know what your test gear is putting onto the panels.

[qrper]

Since it's Solaredge, you can probably narrow down whether it's the panels or just having the optimizers on that section hooked up.
You can disconnect some (or all) of the panel-optimizer connections and see if you still have the same fault.
You can probably add a single optimizer at a time from the "bad" subarray into the "good" subarray. (either increasing the string length by one, or substituting one optimizer for another.)

The problem seems to be within those used modules. Even with my Fluke 77 meter, I can read low resistance between the panel's positive and negative leads shorted together and the array frame.

I purchased an Klein megger the other day. It's not a $1k unit, but not a chinese crap shoot either. Should be here friday, and if the weather holds out, will test the panels one at a time.

[foo1bar]

Nope, I can disconnect one sub array and the fault goes away.

Since it's Solaredge, you can probably narrow down whether it's the panels or just having the optimizers on that section hooked up.
You can disconnect some (or all) of the panel-optimizer connections and see if you still have the same fault.
You can probably add a single optimizer at a time from the "bad" subarray into the "good" subarray. (either increasing the string length by one, or substituting one optimizer for another.)

[qrper]

Could it be on the AC side? I recently had an isolation fault on a SolarEdge inverter and it was the ground wire from the inverter to the main service panel that was the issue.

Nope, I can disconnect one sub array and the fault goes away.

[Ampster]

I believe I may have been over thinking this. It's not so much a ground fault as it is isolation fault. They're close, but not the same. ......

Could it be on the AC side? I recently had an isolation fault on a SolarEdge inverter and it was the ground wire from the inverter to the main service panel that was the issue.

[qrper]

I believe I may have been over thinking this. It's not so much a ground fault as it is isolation fault. They're close, but not the same. The weather here today was crap, so I spent most of the day watching youtube videos. Since my problem only happens when the weather is wet, foggy, rainy, or otherwise nasty, I suspect I don't have a 'wire shorting out' namely because the fault goes away when the weather is better. Yeah, it could be water that getting into a wire or MC4 connector or even one of the optimizers.

I'll still do some more tests, but I leaning toward water that somehow got into the panel (s) and causing the issue.

More tests to do!

that will have to wait until the sun comes back out

mike

[bcroe]

I would check both ends (both disconnected from other equipment) for voltage to ground, If
no voltage found that stuff is not grounded. With voltage I would connect the meter to the
end that is highest, then start disconnecting panels from the opposite end. You need some
higher voltage for a good test, getting that from the panels.

The voltage should hint as to the ground location. If 150V total gives 94V at one end, that
end is likely 2.5 panels away from the ground. Bruce Roe