Thanks dccap & electricpete, The value 0.5 amps is measured via CSH 200 core balance CT connected to a digital relay. These CT's measure directly the earth fault current. So the reading is the actual value of leakage cuurent.
As for an additional megger reading, we did...& the value is good >9...
We are commissioning a new 4.7MW (6.6kV) induction motor. When the motor was tested on no load it was found that there is a 0.5 Amps current as Io. All connections checked & meggered (>9 GOhm), but nothing was found. Still it is showing 0.5Amps Io. Can anyone please advise from where this...