Distribution of Relaxation Times in an Insulating Oil

The dielectric constant and loss of a cable insulating oil has been measured as a function of frequency and temperature. The distribution of relaxation times derived from the data is close to a log-normal (Gaussian in log τ) distribution and is found to be dependent on temperature. The activation energy for dielectric relaxation is non-Arrhenius, similar to the activation energy for viscosity. However, the temperature dependence of both activation energies is found to be significantly different.