AC breakdown characteristics of c-C4F8/N2 gas mixtures in an extremely non-uniform electric field

Abstract

Octafluorocyclobutane (c-C4F8) is one of the environmentally friendly gases with the potential to replace SF6. In this paper, the AC breakdown characteristics of c-C4F8/N2 mixture in an extremely non-uniform electric field were studied; the effects of the gas pressure, electrode distance, and c-C4F8 volume fraction on the breakdown voltage were analyzed; and the feasibility of replacing SF6 with c-C4F8/N2 was verified. The results show that the breakdown voltage of c-C4F8 /N2 increases with an increase in pressure, electrode spacing, and volume fraction of c-C4F8 in an extremely non-uniform electric field. Under the same conditions, the breakdown voltage of 20%c-C4F8/80%N2 is 46–90% that of 20%SF6/80%N2. When the pressure is 0.3 MPa, the 20%c-C4F8/80%N2 breakdown voltage can reach over 57% that of SF6. Taking into consideration the environment, liquefaction temperature, and insulation strength, 20%c-C4F8/80%N2 may replace SF6 used for medium- and low-voltage equipment.