Investigation of the Supercritical Fluids as an Insulating Medium for High Speed Switching

The paper investigates the insulation properties of the supercritical CO2 (SCCO2) fluid as an insulating medium for electrical apparatuses. The insulating material is crucial for electrical apparatuses and SF6 gas has been widely used for high power electrical apparatuses. There have been many research efforts to develop substituents for SF6 gas because of high global warming potential. We obtained above 350 kV/mm insulation strength with 12.0 MPa SCCO2. The positive and negative IEC standard pulses are applied between two 10 mm diameter spherical electrodes. The insulation strength of SCCO2 is at least 2.5 times higher than that of CO2 gas at 6.0MPa. The insulation strength of SCCO2 fluid is about 10 times higher than that of SF6 at 0.5MPa which is the ordinary operating pressure of electrical switchgears. Using the result, we expect that the time for switching and dielectric recovery could be reduced using SCCO2 fluid as an insulating medium.