DC GFCI [RE-wrenches]

[Eric Smiley]

The way I understand it, if there is a ground fault from positive to
ground anywhere between the array and the GFP the connection between the
negative and the grounding system is changed to a high impedance ground
and thus no current flows (ok, a small amount will flow through the
resistor that is now in between negative and ground).
This works only if there is only a single connection between negative
and ground, as there should be.

Could the situation Travis describes occur where there is double ground
fault or short circuit that also creates a fault current in the
grounding conductor?
 Again, the way I understand it with my limited experience with these
devices (They aren't required north of the 49th)... the GFP trips, but
the fault is not cleared. One must rely on the fuses on the module
strings to clear the fault.

A short circuit doesn't pose as much of a problem since current is
limited and not much heat is generated at the fault, but an intermittent
or arcing fault could start a fire.

My 3.2 cents (at current exchange rates)

Eric Smiley - Project Leader
Photovoltaic Energy Applied Research
BCIT Technology Centre

phone: 604.432.8657    fax: 604.436.0286
esmiley at bcit.ca             www.tc.bcit.ca

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