Study of Creeping Discharges Propagating Along a Solid Insulating Surface Immersed in Mineral Oil and Palm Kernel Oil Methyl Ester Under Negative Lightning Impulse Voltage

This article presents the results of an experiment designed to study creeping discharges on a solid insulating surface immersed in palm kernel oil methyl ester (PKOME) compared with those produced from mineral oil (MO). The investigation takes place under standard negative lightning impulse voltage application, and for the three following solid insulating surfaces: hardened glass (HG), porcelain (PO), and simple glass (SG). The distributions of the radial discharge occupancy densities as a function of the thickness of the solid material and the insulating liquid are evaluated. A statistical study of the total and final length of the branches produced by the discharges is presented, as well as the current amplitudes and the charge produced by this phenomenon. A fractal analysis of the phenomenon is also presented. The experimental results show that the distribution of the average radial density of the discharge, the total and final lengths of the branches, and fractal dimension depend strongly on the physicochemical characteristics of the insulation system.