Misleading fault indications [RE-wrenches]

boB Gudgel boB at midnitesolar.com
Tue Mar 4 22:08:48 PST 2008


William Miller wrote:
> 
> 3. Has anyone attempted to detect ground faults by monitoring the 
> difference in current on the positive lead versus the negative?

> BTW, the top study on that page indicates a scenario as you mentioned in 
>  your reply and illustrates the importance of ground fault detection.
> 
> Sincerely,
> 
> William Miller
 
I designedone of these many years ago at Trace Engineering (mid 90s?). 
It was a GFP that looked at the difference between the PV plus and minus 
lines for multiple arrays. Using multiple relays, they shorted out the 
PV arrays and disconnected the 2 output lines from the charge controller 
input.  This also required arc snubbers across the contacts for when the 
relay opened.

  I think it was very close to this time that the small breaker ganged 
with the bigger breaker idea was discovered, which was much cheaper to 
implement, so my GFP never made it to market.



boB Gudgel K7IQ
MidNite/Magnum  Solar/Energy
Washington AC


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