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@hwy17 well, i believe unless i isolate that panel completely from the rest panels, there is a risk that i would close a high voltage circuit with my grounded feet! perhaps the safest approach here is to isolate the panel completely from the array by unplugging the MC4 at the previous and...

Thank you for your comment and information. I am aware of the safety precautions, but let’s forget the insulation resistance for now and focus on measuring the voltage to earth.when a ground fault is present, measurement will show Voc between positive and negative conductors ( dc+ to earth...

@wpns Great find ! I am happy for you My inverter is a 3 phase inverter but not hybrid. I didn’t have yet issues with tripping the AC breaker and the AC wires ( on the right side ) look fine, my issue is that my string inverter shows an isolation error immediately after reboot. let’s...

Yes I know however they should still be able to find if there is an earth fault, according to the inverter‘s manufacturer one should measure voltage between + and - to earth ( must be 0 volt ) And measure insulation resistance between + and - to earth ( without shortcircuit ) and result should...

Yes I have Clamp meter, please correct me if I am wrong : Clamp meters offer a contactless way of measuring current but it can’t measure voltage in a contactless way.

Well, the inverter displays the voltage under load but I don’t think it’s 100% accurate. here is the manual uploaded as pdf as i didn’t find it online in english version ( only in German! ) As I said it’s a German made inverter ( production’s year 2011 or 2012 )

well this is actually a very important tip. My inverter shows an isolation fault after I reboot it! My inverter is a transformer-less ( No Galvanic isolation ) so every morning before it connects to the grid it measures the voltage to earth and if it’s fine it starts producing power. as I...

The error is a typical isolation fault

No it didn’t matter Each string worked fine separately. After reboot I plugged both strings into the inverter but showed an isolation error, before the reboot there was no issue even with both strings plugged in. If I let both strings plugged in overnight, the inverter starts in the next...

@All Thank you for the insightful tips. However there is still a missing piece of puzzle and nobody mentioned it : A current leakage somewhere in the string ( a damaged MC4 or Panel itself ) could reduce the whole current transmitted to the inverter Isn’t this a mechanistically plausible cause ?

The ground wire is the yellow one. I have a 2012 kaco inverter (made in Germany ) it has two MPP tracker, according to the documentation the range is 350-800 volt. I have two strings : string one is connected to MPP1 ( voc 310 volt ) and string 2 is connected to the MPP2 ( voc 620 volt )

Ok,good point! your explanation does make sense. However the documentation contradicts what you saying as the MPP track range is 350-800 volt ! At least that’s what‘s written in the manual !!

Exactly, string one has 10 panels ( voc 31 volt per string ) while string 2 has 20 panels ( voc 31 volt per string ) The panels are the same! My understanding is that the inverter could still work even below the minimal MPP track voltage