Study on static electrification of the PFAE-mineral oil mixture

Abstract

The natural ester of tri-ester type has been implemented on a high voltage large power transformer, rated at 420 kV, since 2014. The high voltage transformer is known prone to the static electrification risk. Palm fatty acid ester (PFAE) which is a monoester oil type has also been tried on the high voltage power transformer. For a retrofilling purpose, some portion of the previously used insulating oil (it is mainly mineral oil) will remain in the transformer. It is then demanded to study the static electrification of a mixture of PFAE and mineral oil. This paper presents an investigation results on the static electrification properties of PFAE-mineral oil mixture at various percentage ratios of PFAE. The results show that charging tendency (ECT) increase with the percentage ratio of PFAE, but then decreases for the oil containing only PFAE. On the other side, the resistivity of oil mixtures decreases with the increase of percentage ratio of PFAE but then increases for the oil containing only PFAE.