Abstract

Future flexible smart-grid power transformers convert DC and wind turbine power to power grid standards using high-frequency transformers to be operated in the 10 to 100kHz range. Fits of AC conductivity and dielectric permittivity as a function of temperature and frequency have been developed for the electrical insulation materials SiO2, Al2O3, Poly Imide. The Debye dipole relaxation equation provides quality fits of the frequency dependence for SiO2 and Al2O3 data of both the real and imaginary parts of the dielectric permittivity data that satisfy Kramers-Konig relations linking the real and imaginary parts mathematically. Poly Imide data has been fit with a modified Debye dipole relaxation equation. The temperature dependence of fit coefficients has been determined and used to generalize the fit to be temperature dependent as well as frequency dependent. AC conductivity as a function of temperature and frequency calculated from the imaginary part of the dielectric permittivity fits for all materials showing that none of these materials meet the needs of smart-grid power transformers of the future according to both Buchanan’s criterion for high temperature electrical insulation materials and Joule heating induced thermal rise calculations.