[RE-wrenches] Megger for array testing

[Drake]

Hello Wrenches,

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.

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.

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:
    * Clamp the Fluke 1587 negative to the enclosuer ground.
    * Put the positive test lead to the negative conductor from the 
array and test
    * Put the positive test lead to the positive conductor from the 
array and test
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.
    * The conductors would be removed from their terminals at the 
inverter and be in free air.
    * The conductors would be continuous through the string of 10 
Sanyo 210 modules.
My questions are:
    * Does anyone see a problem in this approach?
    * 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?
    * Is there any danger to diodes or other PV components?
Thanks in advance.

Drake   
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org/attachments/20101117/e221b0be/attachment-0002.html>