Come on, Bob. It’s a ground fault in the array. Just one more example why ungrounded arrays are FAR safer.
See ya! Marv Director of Technology and Support, North America SolarEdge Technologies, Inc. Tech Support Mobile: +530.798.6770 Mobile: +530.392.0356 From: [email protected] [mailto:[email protected]] On Behalf Of boB Gudgel Sent: Thursday, June 30, 2011 10:19 PM To: RE-wrenches Cc: Nick Vida Subject: Re: [RE-wrenches] how would you measure a partial short circuit On 6/30/2011 8:35 PM, Nick Vida wrote: 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 I'd probably use a DC clamp on ammeter. Clamp on and measure the top and bottom current of each string... What comes in ~should~ come out. If it's much different on one end vs. the other end of one string, maybe that string is conducting around the path somehow. Remember that sometimes just turning the clamp around and measuring the opposite polarity may measure slightly differently than the opposite polarity and that zero calibration is usually necessary. boB 鮑勃 ************************************************************************************ This footnote confirms that this email message has been scanned by PineApp Mail-SeCure for the presence of malicious code, vandals & computer viruses. ************************************************************************************ CONFIDENTIALITY NOTICE: This e-mail and its attachments are intended only for the use of the individual or entity who is the intended recipient and may contain information that is privileged, confidential and exempt from disclosure or any type of use under applicable law. If the reader of this e-mail is not the intended recipient, or the employee, agent, or representative responsible for delivering the e-mail to the intended recipient, you are hereby notified that any dissemination, distribution, copying, or other use of this e-mail is strictly prohibited. If you have received this e-mail in error, please reply immediately to the sender. P Please think of the environment before printing this email
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