Influence of the Electrode Surface Roughness on the Breakdown Strength in Pressurized Synthetic Air at Negative Lightning Impulse Voltage Stress

Abstract:
Pressurized synthetic air is an ecologically friendly alternative insulating gas for gas-insulated metal-enclosed switchgear (GIS). Understanding the discharge behavior is essential for establishing design guidelines for air-insulated GIS. This work aims to find a pressure-dependent relation for the influence of electrode surface roughness in pressurized synthetic air at negative lightning impulse voltage stress. To achieve this, voltage rise tests were conducted at pressures up to 1.0 MPa using an electrode arrangement with a weakly nonuniform field and different surface textures. A simulation model was employed with a single conical-shaped protrusion to calculate the effect of surface roughness. Different electrode surface textures were investigated using a confocal laser scanning microscope to determine the shape of a representative protrusion. The model was applied to predict the breakdown voltage based on the streamer inception voltage. The measured and calculated breakdown voltages are in good agreement for all electrode surface textures investigated.