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