This is an extension of the IR test. In this
test, the two IR measurements are taken, the fi rst reading at 1 min and
the second reading at 10 min. Then the ratio of the 10 min reading to
1 min reading is calculated to give the PI dielectric absorption value.
A PI of winding-to-winding and winding-to-ground should be determined.
A PI below 2 is indicative of insulation deterioration and
cause for further investigation.