PTFE Vapor Contribution to Pressure Changes in High-Voltage Circuit Breakers

A transient magneto-hydrodynamic model based on @Ansys-Fluent software applied on a high-voltage circuit breaker (HVCB) geometry is presented. The model is turbulent (κ-ε realizable model), and radiation is taken into account by a hybrid model (Discrete Ordinates Method and P1). The insulating medium is SF₆, and current I_rms = 25 kA. An ablation model based on the literature was applied to represent the ablation of the Polytetrafluoroethylene (PTFE) walls. The theoretical and experimental results (pressure, ablation rate, and voltage drop variation) are presented and compared. Several cases were considered: no ablation (ceramic walls), ablation only from downstream parts, and ablation from upstream parts of HVCB walls. The corresponding pressure variations are presented. In order to explain the pressure increase, some additional quantities such as mass flow rate and energy integrated into one section of the heating channel are given. The results show that even if the mass of PTFE ablated is small, the pressure increase is due to the energy input from the vapor.