Analysis of AC breakdown of composite-insulation depending on gas pressure and solid insulation thickness

SF₆ gas used widely as insulating component in electric power industry has excellent in insulation and arc extinguishing performance in gas-insulated switchgear. However, the concern about eco-friendly alternative gas is currently rising because SF₆ gas is one of the main greenhouse gases. In this paper, dry-air and composite-insulation (dry-air + epoxy) as the alternative technology for SF₆ gas insulation is studied. Under the gas pressure ranged from 0.1 to 0.6 MPa, the breakdown voltage of dry-air is measured in AC electric field. The data of composite-insulation are ac acquired by changing the thickness of epoxy used in each composite-insulation under the same condition. As a result, in case of dry-air, the gas pressure needs to be compressed as about 3 times as that of SF₆ to maintain the same dielectric strength. When the epoxy is applied by the thickness, the breakdown voltage of composite-insulation is increased by the side of dry-air. However, the difference by the thickness does not exist almost.