Non-Debye Dielectric Behavior of Aged XLPE Cable Insulation

In this study, dielectric responses of aged XLPE cable insulation were investigated. Thermal aging experiment was performed on XLPE sheets cut from 110 kV power cable insulation under 130 degrees C for 10, 20, and 50 days, respectively. The dielectric spectra of all the samples were measured at different temperatures in a frequency range from 10(-1) to 10(6) Hz. An improved analytical methodology, the derivation of real permittivity respect to natural logarithm of angular frequency (partial derivative epsilon'/partial derivative ln omega) was applied in this paper. From experimental results, a new dielectric loss peak appeared in the aged XLPE samples. This new peak showed non-Debye dielectric behavior since it shifted to lower frequency as test temperature increased. Besides, the partial derivative epsilon'/partial derivative ln omega spectroscopy of four samples showed a clear loss peak moving to lower frequency and becoming more intense with increasing aging time while dielectric loss spectroscopy presented blurry information. The non-Debye dielectric behavior of XLPE samples might be related to the movement of large molecular chains under higher temperature. However, further research is required to understand this behavior completely.