Sensing the Aging State of Nomex-Based Nanocomposite Insulation by Dielectric Spectroscopy

This article proposes a methodology to estimate the aging state of the Nomex-based dry-type nanocomposite (NDNC) insulation. For this purpose, seven types of NDNC insulation samples are prepared in the laboratory for experimental investigation. The test samples are undergone through accelerated thermal aging at 145 °C for 600 h in steps of 100 h. The dielectric spectroscopy measurements are conducted on the NDNC-type insulation samples at each aging stages. Three aging sensitive parameters [i.e., transfer function pole (TFP), detrapped charge, and hopping conductivity] are extracted from the experimental results obtained by dielectric spectroscopy [i.e., polarization and depolarization current (PDC) and complex permittivity]. From the experimental results, it is observed that these three parameters are altered with the duration of the thermal aging. This fact signifies that these parameters can be utilized as aging sensitive markers. Therefore, using these three aging sensitive parameters, three empirical relationships are derived to correlate the thermal aging status of the NDNC insulation. Finally, the derived relationships are validated through different sets of test samples having known aging status. Hence, this experimental investigation reveals that the proposed technique can suitably assess the thermal aging state of the NDNC insulation.