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On 6/30/2011 11:35 PM, boB Gudgel wrote:
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On 6/30/2011 8:35 PM, Nick Vida wrote:
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cite="mid:1309491359.76072.YahooMailRC@web112306.mail.gq1.yahoo.com"
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<div>Hi wrenches.<br>
<br>
I had an interesting case today that I have been thinking
about since it happened. I dont have all the details because
the homeownter had to leave before I was done with the
service call, but here is what I do know. SB5000 with 2
strings of 15 modules. String one was 437 vdc, and string 2
was 247vdc. I decided to look for a ground fault, and I
turned off the inverter. I measured for ground faults and
found no evidence of anything wrong in that regard. As the
homeowner was out of time and wanted me to go, I re-landed
the wires in the dc disco, and when I replaced the fuses, I
noticed a minor arc when one of the fuses was going it.
Although I had no time to measure it, I think that there
might be a partial short circuit, possibly with one complete
string and some panels of the other string, and the
remaining panels on the second string. My mind was racing
with how I could have measured for a partial short circuit
without seeing it as an arch. I can imagine such a thing on
a bigger system being a dramatic electrical event. <br>
needless to say, I cant wait to get back there and go
through the signal path properly and find out what the
electrician did. And of course i realized that replacing the
fuses in such a questionable situation was probably not the
best idea.<br>
Do any of you have any thoughts on how one would measure for
such a thing?<br>
<br>
nick vida</div>
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<br>
<br>
What does this part of your question mean ??<br>
<br>
"<span style="font-family: "Courier New";"> I noticed a
minor arc when one of the fuses was going it."<br>
<br>
</span></blockquote>
<br>
I see what you were saying. When the fuse was going "IN" ... Into
the fuse holder.<br>
<br>
Could it be that the inverter was connected (but turned off
otherwise) and it arced as the inverter input capacitors were
charging up ?<br>
<br>
If so, then the current would die to nothing soon after the fuse was
in place. A clamp meter would show<br>
that too.<br>
<br>
boB<br>
<br>
boB<br>
<br>
<br>
<br>
<br>
<br>
<blockquote cite="mid:4E0D6ABF.7030001@midnitesolar.com" type="cite"><span
style="font-family: "Courier New";"> boB<br>
<br>
</span><br>
<br>
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