Electrical Breakdown of N20-SF6, N20-CCL2F2 and N2O-CO2 Gas Mixtures

Using 112 mm diameter, Harrison profile stainless steel polsihed electrodes, uniform field dc breakdown voltages are measured for N2O mixtures with SF6, CCl2F2, and CO2 in the pressure range of 0.02 to 1 MPa and gap lengths up to 20 mm. The results show that the breakdown strength (E8/P) of SF6, CCl2F2 and their mixtures decreases with pressure while it remains practically constant for N2O and N2O-CO2 mixtures over the investigated pressure range. From the breakdown data, limiting sparkover strengths (E8/P)lim are calculated for various mixtures which are expressed by a general expression (E8/P)lim = A+B (X)C, where X is the percentage content of SF6 in SF6-N2O mixtures, CCl2F2 in CCl2F2-N2O mixtures, and N2O in N2O-CO2 mixtures. Values of constants A, B, and C are given for the investigated gas mixtures.