The Effect of Pressure and Gap Distance to AC Breakdown Behavior of SF6/N2 Gas Mixtures

Abstract

To date, sulphur hexafluoride (SF 6 ) gas has been the predominant insulation medium in high voltage applications which mainly due to its exceptional physical and electrical properties. However, environmental concerns arise since SF 6 is a potent greenhouse gas. In this study, the breakdown behavior of SF 6 /N 2 gas mixtures under non-uniform field is investigated. A breakdown voltage test on SF 6 /N 2 gas mixtures which subjected to AC voltage was conducted inside a pressure vessel. The gas mixture ratio was fixed to 10/90, while the total gas pressure was varied between 0.11 MPa to 0.15 MPa with 0.01 MPa intervals. Meanwhile, R6-Plane electrode configuration was used to produce a non-uniform field where the electrodes gap distance was varied between 5 mm to 30 mm. The results show that the breakdown voltage of SF 6 /N 2 (10/90) gas mixtures increases linearly with the increase of gas pressure and electrodes gap distance. However, it is found that the effect of electrode gaps distance is more dominant to cause the breakdown voltage of SF 6 /N 2 gas mixtures to increase, as compared to the effect of small range of pressure levels.