AC Breakdown Characteristics of c-C 4 F 8 /N 2 Gas Mixtures in an Extremely Non-Uniform Electric Field

Octafluorocyclobutane (c-C 4 F 8 ) is one of the environmentally friendly gases with the potential to replace SF 6 . In this paper, the AC breakdown characteristics of c-C 4 F 8 /N 2 mixture in an extremely non-uniform electric field were studied; the effects of the gas pressure, electrode distance, and c-C 4 F 8 volume fraction on the breakdown voltage were analyzed; and the feasibility of replacing SF 6 with c-C 4 F 8 /N 2 was verified. The results show that the breakdown voltage of c-C 4 F 8 /N 2 increases with an increase in pressure, electrode spacing, and volume fraction of c-C 4 F 8 in an extremely non-uniform electric field. Under the same conditions, the breakdown voltage of 20%c-C 4 F 8 /80%N 2 is 46–90% that of 20%SF 6 /80%N 2 . When the pressure is 0.3 MPa, the 20%c-C 4 F 8 /80%N 2 breakdown voltage can reach over 57% that of SF 6 . Taking into consideration the environment, liquefaction temperature, and insulation strength, 20%c-C 4 F 8 /80%N 2 may replace SF 6 used for medium- and low-voltage equipment.