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<DIV><FONT size=2 face=Arial>Hello Drake,</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>I think you should talk to a Sanyo Solar
engineer to get accurate information. Every Sanyo and other brand UL
listed modules must be dielectric voltage-withstand factory tested to 2 times
system voltage plus 1,000 volts. I hi-pot test modules in the factory at
3,000 volts so they will meet UL and also IEC standards. I megger field test
arrays at 1,000 volts to find module, connector, and wiring problems. Megging at
500 volts is ok, but it may not reveal wire insulation problems.</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>Joel Davidson</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
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style="BORDER-LEFT: #000000 2px solid; PADDING-LEFT: 5px; PADDING-RIGHT: 0px; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px">
<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="FONT: 10pt arial; BACKGROUND: #e4e4e4; font-color: black"><B>From:</B>
<A title=drake.chamberlin@redwoodalliance.org
href="mailto:drake.chamberlin@redwoodalliance.org">Drake</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A
title=re-wrenches@lists.re-wrenches.org
href="mailto:re-wrenches@lists.re-wrenches.org">RE-wrenches</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Wednesday, November 17, 2010 7:36
AM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> [RE-wrenches] Megger for array
testing</DIV>
<DIV><BR></DIV>Hello Wrenches,<BR><BR>Looking through the archives on using a
Megger for testing modules, it appears that it is best to keep voltages
to 500VDC. I read all that I could find. <BR><BR>Talking to a Sanyo
representative, I was told that keeping test voltage under 600 would not void
the warranty or be an issue with UL. He said they have tested Sanyo
modules up to 1000 VDC with no problems.<BR><BR>As a final test on a system, I
want to Megger test the array from the terminations at the inverter. The
approach I'd plan to use is:
<UL>
<LI>Clamp the Fluke 1587 negative to the enclosuer ground.
<LI>Put the positive test lead to the negative conductor from the array and
test
<LI>Put the positive test lead to the positive conductor from the array and
test </LI></UL>All tests would be done at 500 V. The modules are
illuminated, but there is no significant reading from either positive or
negative terminal to ground.
<UL>
<LI>The conductors would be removed from their terminals at the inverter and
be in free air.
<LI>The conductors would be continuous through the string of 10 Sanyo 210
modules. </LI></UL>My questions are:
<UL>
<LI>Does anyone see a problem in this approach?
<LI>Since the array often has 500 VDC open circuit readings and shows no
indication of a fault whatever, would this test accomplish anything more
than the standard voltage to ground tests I've already done?
<LI>Is there any danger to diodes or other PV components? </LI></UL>Thanks in
advance.<BR><BR>Drake
<P>
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