Frequency spectrum of radiation transfer in high voltage circuit breaker arcs for polymer nozzle ablation in C₄F₇N and CO₂ gas mixture

Abstract

Arc radiation-induced polymer nozzle ablation plays a crucial role in the operation of self-blast circuit breakers. Up to now, there is no study specifically on the spectral distribution of radiated power from a switching arc towards the nozzle surface and its implication to nozzle ablation. Three-dimensional radiation transfer calculation has been performed in this study for arcs burning in the mixture of C4F7N+CO2+PTFE, a gaseous environment that is under significant focus in the development of SF6 free switching technology to aim net-zero by the middle of this century.
Results show that photons from infrared to extreme ultraviolet (UV, up to 5×10^15 Hz) are emitted from the core of high current arcs. However, the high-frequency photons are mostly absorbed within the arc column, especially at the arc edge, and only photons up to 1.7×10^15 Hz (far UV, 7 eV) can penetrate the arc edge and cold gas and reach the nozzle surface. The spectral distribution of the radiative energy at different instantaneous currents (15 kA, 28 kA and 60 kA peak) and different locations of the nozzle is presented and compared in detail. The location of the radiation absorption zone at the arc edge and the radiative power reaching the nozzle wall as a function of the instantaneous current is, in particular, purposely considered.