Theoretical and Experimental Analyses of the Synergism in the Dielectric Strength for C3F8/C2HF5 Mixtures

Two theoretical approaches are applied in order to describe the behavior of the experimental breakdown voltage in C3 F8 C2 H F5 mixtures. First, available cross section data of the electron-molecule processes are scaled to simulate the dielectric strength (DS) behavior in both C3 F8 and C2 H F5 gases at the level of the Boltzmann equation (BE) solution corresponding to a homogeneous electric field model. Then, the DS of C3 F8 C2 H F5 mixtures is evaluated and compared to the experimental breakdown voltage measured using different electrode geometries as sphere/plane type via experimental techniques, i.e., power frequency and negative or positive polarity lightning impulse. Due to the limitation of the BE approach to describe the observed experimental data, the Hunter-Christophorou [J. Appl. Phys. 57, 4377 (1985)] model regarding the positive synergism phenomenon is finally applied. Both models allow us to compare relative values of the "chemical" and "physical" DS components in C3 F8 C2 H F5 mixtures. © 2007 American Institute of Physics.