Lightning and switching impulse breakdown of rod/plane gaps in nitrogen and nitrogen/freon (CCl2F2) mixtures

Lightning pulse (1.5/50 \mus) and switching pulse (200/2000 \mus) breakdown phenomena in N and N/Freon mixture were investigated in rod/plane gaps at total pressures \leq5 bars and spacings \leq100 mm, with freon concentration of 1-20%. In general, substantial improvement in breakdown strength can be achieved, particularly for neg. polarities, with the addition of small percentages of $CCl_2F_2$ to $N$. The characteristic pressure effect in the pos.-point breakdown voltage vs. pressure curve obsd. in many strongly attaching gases is ill defined in these mixtures, and can be seen only over a limited range of experimental conditions. The corresponding effect for negative-point breakdown is observed in these mixture at 2-4 bars for long gaps (>40 mm). The breakdown voltages for a 100-mm gap with the switching pulse at pressures >2 bars are generally 20% lower than the corresponding lightning pulse data.