Trifluoroiodomethane（CF

3

I） has been broadly proposed as a potential replacement for SF

6

.AC breakdown tests on CF

3

I-N

2

gas mixtures have been completed in the condition of quasi-homogeneous and extremely non-uniform electric field

focusing on the CF

3

I-N

2

gas mixtures with volume fraction of 20% and 30% CF

3

I

gas pressure from 0.1 MPa to 0.3 MPa

and gap distance from 5 mm to 30 mm.On the basis of the foregoing analyses of breakdown characteristics

we reveal the effect laws of CF

3

I volume fraction

gap distance

gas pressure

and electric field non-uniform coefficient on the power frequency breakdown voltage of CF

3

I gas mixtures.The AC breakdown voltages of CF

3

I-N

2

gas mixtures linearly increase with the gas pressure and gap distance under quasi-homogeneous field.In the condition of non-uniform field

the AC breakdown voltages of CF

3

I-N

2

gas mixtures approach to saturation with the increasing of gas pressure.The experimental results indicate that CF

3

I-N

2

gas mixtures with CF

3

I volume fraction of 20% and 30% can achieve nearly 50% and 55% power frequency withstand voltage of pure SF

6

respectively.