[RE-wrenches] how would you measure a partial short circuit

[Nick Vida]

Hi wrenches.

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. 

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.
Do any of you have any thoughts on how one would measure for such a thing?

nick vida
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