[RE-wrenches] Finding ground faults

[Bob Clark]

Wrenches:

 

Sorry to bring up this situation again, but I could not find a previous
discussion thread that talked about step-by-step procedures for tracking
down ground faults (I believe it was John Berdner who provided the bulk of
the writing in that regard and it related to high voltage strings-not that
75-85 volts per string is all that low).

 

We have an Outback FLEXpower Two system with 8, 3-module strings (Silicon
Energy 190W, 25.3Vmp, 7.5 Imp) combined in a Midnite Solar MNPV12 combiner
with breakers.  The cables from the array are routed to two different Wiley
4-string pass-through boxes (located under the two center strings) and then
off of the roof and into the PV combiner.

 

Up until this week the system has seen several weeks of awesome power
production.  Yesterday, the rains came and the GFDI breaker tripped.  Every
time it rains, the little green breaker on the GFDI trips off.  That tells
me that the ground fault is occurring in a place where at least one of the
conductors on one of the strings (possibly more) is getting wet and
conducting current to ground.

 

It would seem to me that the most likely place for moisture to cause a
ground fault to occur in this system would be in the pass-through boxes.
This would mean removing the central modules to access the pass-through
boxes.

 

Any of you who have mounted the Silicon Energy modules know that the cables
are contained in trays along the side of the modules until they are routed
through conduit to the pass-through boxes.  So, if there is current going to
ground from any of these cables, it could even be occurring in any of the 9
trays along side of the modules.  I do not like the idea of tracking down a
ground fault in one of these trays as they are all interconnected.

 

How best (and safely) to track down where the ground fault is occurring?
Any advice as to the best and safest way to track down the ground fault(s)
would be greatly appreciated.

 

Bob Clark

SolarWind Energy Systems, LLC

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