Bob I had a tough find one time, when it rained I would have GF when it would
dry out no GF
I turned off main DC disconnect, I turned off each circuit breakers for the
strings, I opened the grounded conductor of the strings, I connected my Megger
at 500 volts I think It might have been maybe 1000 volts, after the fault
cleared, the megger found one string that was bad and I located the problem in
a J box
________________________________
From: Steve Higgins <shigg...@outbackpower.com>
To: RE-wrenches <re-wrenches@lists.re-wrenches.org>
Sent: Wednesday, May 23, 2012 11:27 AM
Subject: Re: [RE-wrenches] Finding ground faults
Bob,
Be careful with that GFDI... It's most likely wired on the output of the
controllers, on the battery side.
This can trip if a ground fault is occurring, or if you are exceeding 80 amps
of current. With 8, 3 module strings, an edge of cloud event you could have
the 80amp portion of that breaker tripping rather than the GFDI.
Steve Higgins
Sales Application Engineering Mgr
Direct 360-618-4313
Outback Power Technologies
5917 195th Street NE Arlington, Washington 98223
________________________________
From: re-wrenches-boun...@lists.re-wrenches.org
[mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Bob Clark
Sent: Tuesday, May 22, 2012 7:37 PM
To: re-wrenches@lists.re-wrenches.org
Subject: [RE-wrenches] Finding ground faults
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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