Experimental and calculation study on insulation strength of C4F7N/CO2 at low temperature

In this paper, the insulation strength of C
₄
F
₇
N/CO
₂
with temperature is obtained by AC breakdown tests and theoretical calculations. The experimental results with 9%C
₄
F
₇
N/91%CO
₂
at 0.7 and 0.5 MPa pressures show that the breakdown voltage changes nonlinearly with temperature. Theoretical analysis shows that the nonlinear change is caused by liquefaction of C
₄
F
₇
N. The critical electric field of C
₄
F
₇
N/CO
₂
is calculated based on the streamer discharge theory. A calculation model is established to calculate the usable pressure of C
₄
F
₇
N/CO
₂
and the mole fraction of C
₄
F
₇
N at given minimum temperature, which can provide reference for its practical application.