Assessment of dielectric insulation condition of power transformers using Dielectric Absorption Ratio (DAR) and Polarization Index (PI)
DOI:
https://doi.org/10.56143/9c2hq029Keywords:
Dielectric Absorption Ratio (DAR); Polarization Index (PI); transformer insulation diagnostics; moisture assessment; dielectric response; solid insulation aging; time-domain insulation testing; insulation resistance; transformer condition monitoring; dielectric degradationAbstract
The operational reliability and service life of power transformers significantly depend on the condition
of their solid dielectric insulation. Moisture ingress, thermal aging, and electrical stress alter the dielectric
properties of insulation, reducing its electrical strength and accelerating degradation processes. This
paper examines two widely used diagnostic indicators—the Dielectric Absorption Ratio (DAR) and the
Polarization Index (PI)—which are employed to assess insulation moisture content and aging degree.
The diagnostic criteria, interpretation of measured results, and significance of these indicators in
predictive maintenance are presented.
