Breakdown Characteristic of N2-CO2 Gas Mixtures under AC and DC Test Voltages

Abstract

Abstract This study provides fundamental knowledge on the breakdown properties of N2-CO2 gas mixture with a ratio of 20:80, 50:50, and 80:20. The gas mixtures were tested under HVAC and HVDC voltages with 1 bar (abs) pressure. The plane-plane and needle-plane electrodes were used with gap lengths between 0.5 cm to 2.5 cm. It is found that the breakdown voltage of N2-CO2 mixture increased with the increased of CO2 content. The breakdown voltage is also affected by the increment of gap distance for both electrode geometrics; plane-plane to represent the uniform field and needle-plane as the non-uniform field. The gas under uniform field configuration has a higher ability to withstand higher voltage levels compared under non-uniform field configuration. However, the non-uniform field provides a very high electric field intensity, which implies very high electric field stress. By increasing the percentage CO2 in N2-CO2 mixture, the insulation strength can reach about 64% that of pure SF6 gas at the 0.1 MPa.