[RE-wrenches] Megger for array testing

[Joel Davidson]

Hello Drake,

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.

Joel Davidson

  ----- Original Message ----- 
  From: Drake 
  To: RE-wrenches 
  Sent: Wednesday, November 17, 2010 7:36 AM
  Subject: [RE-wrenches] Megger for array testing


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

  Drake  


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