Depolarization index for dielectric aging indicator of rotating machines

The term Depolarization Index (dP.I.) for rotating machines is introduced in this article as an additional information to the time-domain and frequency-domain dielectric response results for gaining high-precision interpretation and identification of some types of aging in solid dielectrics, particularly the non-restoring thermal trouble and insulation abrasion. Factors affecting the correctness and accuracy of dP.I. are discussed. The dP.I data from 60 medium-to-large generators and 117 large industrial motors, in Asia-Pacific were analyzed to provide the conclusion.