Solar inverter caused DF breaker tripping and strobing LEDs

11bgrunt

Pragmatist
Location
TEXAS
Occupation
Electric Utility Reliability Coordinator
Ran on a voltage complaint for Square D Homeline dual function, 120V breakers in a sub-panel, trip randomly and will not stay on. White pigtail version.

House is 16 years old and only the five DF breakers tripped randomly.

In the testing, the breakers were removed from the energized buss, leaving the pigtail attached to the neutral buss. The DF breakers continued to trip.

Neighbor was inquisitive and got involved. He had lived there one week. LEDs were flickering/strobing throughout his house, his DF breakers were tripping, and other types were buzzing. Fan remotes were going on and off and GFCI plugs wouldn’t stay on. He had just transplanted from Cali and didn’t know what normal was. This house has 4kW of roof mount, grid-tie solar. It was a beautiful day, and the solar panels had full exposure.

A Fluke 345 PQ meter let us see the I&E waveform. The house with solar is fed by the same 50kVA POCO padmount as the original complaint.

Load was dropped by tripping breakers while watching the waveform. When the only thing left was the solar tie, we opened the solar disconnect and every issue went away in both houses.

NEV was checked and never went over 1.5V. The picture shows the 345 parked on a conduit. I haven't learned how to measure current through a steel conduit yet and still have to check each conductor the old school way.

Help me understand what part of the inverter can fail and cause this.

SolarEdge.JPG
 
Theoretically it could be inverter itself. Like, the actual power electronics, possibly. It ought to be unlikely for problems that bad on a listed inverter, where the inverter still operates. It's pretty moot to you since you're not going to fix the thing, just replace it if they RMA. Not super surprised it's Solaredge, I'm glad I don't work with that brand anymore.

It's possible the inverter isn't 'failing' per se but that you're seeing some more mysterious interaction between the grid, inverter, and other items.

That inverter is 10 or more years old.
 
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