Physico-chemical properties of transformer mineral oils submitted to moisture and electrical discharges

Abstract

This work is devoted to an accurate investigation on the variations of the physicochemical properties of three transformer mineral oils of different levels of degradation submitted to moisture and electric discharges. The first one is a non treated new oil while the second is taken from a one year normal operating transformer and the third is extracted from a 15 years old operating transformer. The investigated parameters are breakdown voltage, relative permittivity r , dissipation factor (Tan) and resistivity. Each oil peculiarities are determined through these parameters. Measurements on an on load operating transformer are reported to validate some laboratory obtained results.