Influence of Temperature and Moisture on the Dielectric Response of Oil-Paper Insulation System

Since a few years, non-destructive techniques for assessment of power transformer insulation systems have been developed. The dielectric response in time and frequency domain is studied to determine the oil/paper insulation condition. One of the important parameters affecting the dielectric response is the temperature. On real transformer, the temperature of measurement is not controlled and is usually related to ambient temperature, therefore in order to compare measurements at different temperature it is important to study the influence of this parameter. It is well know that the temperature dependency to the response of transformer insulation follows an Arrhenius type law and that it is possible to normalize to a master curve measurement taken at different temperature. To evaluate this dependency and to model it, this study was done on transformer model with both the dielectric response in time and frequency domain with the temperature varying from 10 to 50 degC. The results allow us to model the dependency of the temperature and to calculate the activation energy.