Ageing Estimation of Transformer Oil by Ladder Phenomena

In this work, condition of acid aged transformer oil based insulation is assessed. For this purpose, three types of oil insulation (Mineral oil, Natural Ester and Synthetic Ester) are selected as base oil. In addition, formic, acetic and levulinic acids are chosen to prepare different aged insulation. Therefore, the prepared samples are subjected to a non-invasive FDS test to obtain important dielectric parameters such as AC conductivity and dielectric loss. It is observed from the AC conductivity profiles that it exhibits an imperative property i.e. “Ladder phenomena”. Considering this phenomenon, different threshold frequencies are calculated and found to be aging sensitive. Therefore, the impact of acid ageing corresponding to different polarization and relaxation mechanisms are discussed using those novel aging sensitive parameters.