Analysis of dielectric response of epoxy-mica insulation with temperature normalization

To decrease equipment costs and facilitate the simple and convenient on-site frequency dielectric spectroscopy (FDS) testing of epoxy-mica insulation of stator coils, specimens from a stator coil, subjected to 623 hours of 48 kV AC electrical ageing, were tested at temperatures from 0 to 120°C and frequencies from 10
^-1
to 10
⁷
Hz. The master curves and shift factors of the real and imaginary susceptibility components were obtained by the temperature normalization method. According to the horizontal shift factor, the complex susceptibility of the insulation increased exponentially with temperature. Regarding the vertical shift factor, the characteristic peak of the imaginary component of the complex susceptibility, representing the interface polarization of the epoxy-mica insulation, increased exponentially with temperature, and its movement can be expressed by the Arrhenius equation. The master curves of the temperature from 20 to 100°C and the frequency from 1 to 10
³
Hz can be fitted to the six-degree Debye relaxation model and Havriliak-Negami function. Through the shift factors and master curves, FDS data from 20 to 100°C can be estimated without temperature control.