On the Simulation of Bifurcated Paschen’s Curves for Non-Uniform Fields in Air

Paschen’s curves are essential for understanding the behavior of gas insulation systems in uniform field gaps under different pressure conditions. However, most real-world insulation systems generate non-uniform fields. For electrode geometries that generate non-uniform fields, corona discharges tend to occur at lower voltages than required for complete air gap breakdown, particularly at high pressure–distance product values. This paper presents a physically based formulation to describe and predict observed Paschen’s curve bifurcation in non-uniform electric fields under different pressures, specifically focusing on rod-plane and sphere-plane electrode geometries. This method uses finite element analysis (FEA) to map the electric field distribution and applies the effective first Townsend coefficient taken from the open-source LxCat database and Meek’s breakdown criterion for non-uniform fields. Despite its simplicity, the reduced physics model presented in this paper successfully predicts Paschen’s curve bifurcations at different pressure levels for the investigated non-uniform field gaps. These bifurcations distinguish between corona discharges in non-uniform field configurations and complete air gap breakdown. The proposed method is of interest for the design of insulation systems, especially in demanding environments like the aerospace industry.