DC GFDI / trouble shooting ground faults. [RE-wrenches]

[John Berdner]

Wrenches:

AS long as we are grounding our PV arrays here in the US (that is a long
debate for another time) I think we need some form of GFDI.

The DC GFDI required by 690 is intended for fire protection, not
personnel protection.
The main goal is to prevent overheating and fire in of inadvertent
conductors, e.g. metal roofing.
Without the GFDI, if the array ground faults then the full array current
could flow through the fault path and not through the grounded
conductor.
I agree with C. Freitas on this one, the costs are pretty small and the
GFDI tells you that something is wrong.

In the Sunny Boy, the inverter start up sequence requires you to
ungrounded the array so the inverter can measure for leakage to ground
(megger test).
Once the inverter sees the array is truly isolated from ground then it
tells you to put the GFDI fuse in and the inverter will start up.
Like Chris, I find that ground faults are responsible for the majority
of our customer service calls.
Since ground faults are so had to track down we often send out new
inverters under warranty.
When the GFDI problem inverters get back here, we can't find anything
wrong with most of them.
In my experience tracking down ground faults is not well understood and
is really hard to figure out.
I think everyone could benefit from some helpful hints that others have
used.

I would like to know how wrenches out there are trouble shooting ground
faults ?
What procedures do you use ?
What tools or meters do you need ?

If you have any questions or I can be of any further assistance please
do not hesitate to contact me.

Best regards,

John Berdner

SMA-America, Inc.
20830 Red Dog Road
Grass Valley, CA  95945
Tel: 530.273.4895
Fax: 530.274.7271

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