Investigation on the Effect of the Cross-Section of Insulators on the Radial Discharge Distribution of Creeping Discharges

Divergent electric fields on the solid/liquid interfaces of oil-filled assets can lead to the propagation of the creeping discharges over the interface. Therefore, it has become an interest of the researchers to analyze creeping discharges in a laboratory environment for the design optimization of high voltage assets. Over the past decade, studies have been carried out to analyze creeping discharges using both experimental and simulation models. It has been observed that the shape of the interface effects on the propagating pattern according to simulation and experimental studies. This work is aimed at the study of the effect of the shape of the cross-section of the insulators on the radial discharge distribution of creeping discharges using a test apparatus and a simulating model. The test setup is based on a point plane electrode system and required solid/liquid interfaces are created by immersing the prepared insulating samples with two different cross-sections in the dielectric liquid. A model is formulated in a Laplacian field and the pattern propagates in a stepwise manner depending on the electric field distribution of the area enclosed by the boundaries of different shapes. It can be seen that the maximum value of the radial discharge distribution of the pattern can be observed in-between the center of the pattern and the edge of the interface and that point moves toward the boundary of the insulator as the applied voltage increases. It can be seen that the distribution corresponding to the square cross-section is higher than that of the circular cross-section around the center of the propagating patterns while simulation studies show that radial discharge distribution is independent of the shape of the cross-section. The study shows that experimental studies regarding the effect of the shape of the material cannot be replaced with simulations even if it may provide a theoretical foundation to analyze creeping discharges. However, the work reveals that it is better to consider the total area of the pattern instead of the distribution of the pattern to evaluate the damage done by the discharge for different kinds of insulator shapes.