Testing transformers with a megger 1

[jonathn1]

Recently had a boss tell me to look over a procedure. he had us testing using a megger with red and black leads. We are asked to use the red lead to ground and the black lead to the power connection for each phase.
My recommendation was to switch the leads locations so the black was on ground and red for the power connections. Stating that altho it wouldnt change the test results it did enable good habits for any later tests, since we are not working with electricians doing these tests.
He came back saying a test was done in France on this. They actually proved that changing the leads so the black was on the power, or phase connections, and the red was on the ground connection gave a significantly better reading. it had to do with aligning the electrons and providing a secure field.
Has anyone heard of a test like this or any kind a validity to it?

 

[ScottyUK]

If this is a big transformer then you might want to do some research on the PI, or Polarisation Index, test. That can be a useful test when evaluating HV insulation.


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