Insulation resistance and polarization index tests are important diagnostic tools for determining the condition of transformer insulation. These tests are used to identify any issues with the insulation, which can help prevent catastrophic system failures and extend the life of the transformer.
Testing of insulation resistance and polarization index shall be carried out under
Apply the test voltage (5KV DC) on the following Connection and note down the readings
Two Winding Transformer
HV – Earth
LV – Earth
HV-LV
Three Winding Transformer
HV – Earth
LV1 –Earth
LV2 –Earth
HV -LV1
HV -LV2
LV1 -LV2
The insulation resistance measurement is done from 15 seconds to 1 minute with 15 15-second interval and then for every minute up to ten minutes. The value obtained at 10 minutes divided by value at 1 minute gives the polarization index
performing insulation resistance and polarization index tests on transformers is an essential part of preventive maintenance. These tests can help detect any issues with the insulation and prevent costly failures. It's important to follow proper safety procedures when working with high-voltage systems, and always consult a qualified professional if you have any dou