Partial Discharge Inception Voltages of Transformer Liquids under Various Electric Field Conditions

The majority of the research concerning partial discharge (PD) characteristics of insulating liquids employs needle-to-plane or needle-to-sphere electrode systems that generate highly divergent electric fields. This is because in such electric fields, discharges can be easily initiated without leading to electrical breakdown. However, the insulating liquid filled in a large power transformer is typically subjected to uniform or quasi-uniform electric fields. This research comparatively investigated the PD inception voltages of three transformer liquids, including Gemini X (a conventional mineral oil), Diala S4 ZX-I (a synthetic hydrocarbon liquid manufactured through gas-to-liquids processes) and MIDEL 7131 (a synthetic ester), under various electric field conditions. To alter the electric…