DC GFCI [RE-wrenches]

[Drake Chamberlin - Electrical Energy]

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The ground fault detector is near the batteries not the array.  In the 
event of a nail through a cable, shorting positive to ground, wouldn't the 
circuit from the array continue to short even if the device were tripped?

Drake

At 02:58 PM 01/11/2002 -0800, you wrote:
>Travis,
>
>On a line-to-ground fault, the grounding path is removed and therefore the
>return path for the fault current is broken. Again, it doesn't solve all
>faults, just those that are more likely to happen. Historically, ground
>faults have been the source of failures of older arrays and various wiring
>mistakes.
>
>If you bolt the positive and negative together (e.g. with a metal staple
>through both--good reason never to use metal staples), the GFP may not
>detect this fault, but the inverter likely will because most inverters
>detect array shorts. If it is a battery-based system, the reverse current
>from the battery will normally trip the main breaker.
>
>Can you think of a fault that isn't covered? I'm sure there are some high
>impedance line-to-line faults that might go undetected, but they will likely
>deteriorate into one of these other faults and cause a trip. All-in-all, the
>GFP fills a major gap in detection of faults that normal overcurrent
>protection is likely to miss.
>
>Bill.
>
>
>
>-----Original Message-----
>From: Travis Creswell, Ozark Solar [mailto:ozsolar at ipa.net]
>Sent: Friday, January 11, 2002 12:33 PM
>To: RE-wrenches at topica.com
>Subject: Re: DC GFCI [RE-wrenches]
>
>
>I never did understand what it's protecting.  I don't remember anything
>about a Canadian lab questioning them.  That does sound an awful lot like
>what I posted, though.
>
>The main problem I saw, and still do see with them was as such;
>
>A fault happens somewhere in between the inverter and the roof mounted
>panels.  The GFP detects this fault and opens the circuit.   Since the
>panels are still producing power the fault is still merrily smoldering away
>on the roof or in the attic until sunset.  Hopefully the customer notices
>the breaker is tripped before the house catches fire.
>
>Wow, now that's helpful a device.
>
>Travis Creswell
>Ozark Energy Services, Inc.
>----------
> >From: Drake Chamberlin - Electrical Energy <solar at eagle-access.net>
> >To: RE-wrenches at topica.com
> >Subject: DC GFCI [RE-wrenches]
> >Date: Fri, Jan 11, 2002, 1:08 PM
> >
>
> >Long ago, someone on the list mentioned that personnel in a Canadian Lab
> >felt that the DC GFCI, mounted near the batteries, for roof mounted systems
> >wasn't an effective safety device.
> >
> >Does anyone remember the reference on that?
> >
> >Thanks,
> >
> >Drake
> >
> >
>
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