P.i. Of Turbogenerator

[PRADIP]

During testing of a 500MW turbo-generator(21KV), it is found that the 60secs & 600secs insulation resistance(IR) of stator wdg.(each phase) is 56 giga ohm(in both 60secs & 600secs) measured by the 5kv megger(keeping other two phase grounded,guard wire of megger connected to generator manifold.)
So the P.I.= 1,
Again, the said value is 26 giga ohm(in both 60secs & 600secs) measured by the 2.5kv megger(other connections remain same).
i,e, P.I.=1.
IS IT ACCEPTABLE ?
ARE THERE ANY SIGNIFICANCE OF "P.I." AT SUCH HIGHER VALUE OF IR ?
WHAT IS "P.I." IN-TERMS OF MOLECULAR THEORY / PHYSICAL CHEMISTRY?

 

[zog]

PI values are irrevelant at those high IR values.

PI is a measure of the rate of decay of leakage current, after 10 minutes you should only be measuring leakage current and no polarization and/or absorbtion current.