ARC fault

[msi99]

Thanks! Interesting distinction between parallel vs series arcs.

The one time I found an arc, it was at a PV panel-to-panel series connection. Not too evident by looking at it though. Slightly deformed possibly.
The MC connectors had melted themselves together. When pulling it apart they would not budge or crumbled in my hands, the metal ripping out of the plastic housing. They were burnt to a crisp.

That is what I will start by looking for: MC conns that don't pull apart.

This could also have occurred if the connectors on the panel are not from the same manufacturer as the connectors on the optimizers. ( SMA) Please note that most of the module spec sheets show that they are MC4 compatible but they might be made by a different manufacturer.

 

[coop3339]

You could try IV curve testing and look for a sort of a lighting bolt shape on the vertical part of the curve. This indicates a failing bypass diode. I have seen this cause a lot of intermediate arc faults that are difficult to find. If its a bad connector, it would probably cause some increased resistance. This can be indicated by a more slopped horizontal portion of the curve.