Partial discharges and surface potential at fissure-like solid-solid interface

Surface potentials at fissure-like interface formed by two epoxy resin blocks were studied after PD occurring in air gap in series with the interface at the room temperature. The negative potential was detected at the zero-cross point of ac applied voltage from negative to positive after negative PD occurred during the previous negative half-cycle and the positive potential was detected in the reverse case. Surface potentials, caused by charge deposition from PD, were found having a close relation to PD magnitude. Comparing the positive surface potential to the negative one, their surface potential values and distributions on the interface had some differences. Different PD statuses between positive PD and negative PD are thought to be one of the important factor Positive PD are considered to crawl into the interface through the air gap from the needle-electrode while applied voltage increased and positive surface potentials as well as PD characteristics were susceptible to the surface roughness. Roughened surfaces are supposed to have a higher capacity of charge deposition due to their higher surface potentials and wide gradual potential distributions on the roughened interface.