Spectral and spatial characteristic behaviour of three-dimensional radiation transfer in SF6 switching arcs

Abstract

Abstract The spectral and spatial characteristics of three-dimensional radiation transfer across an arc column of 0.08 m long, typical in high-voltage gas blast circuit breakers, has been studied in detail. The arc column under study corresponds to an instantaneous current of 15 kA in SF6 gas at a pressure of 10 bar. Our results show that to calculate the radiative flux divergence (as a volumetric energy source), only a segment of the arc column of 0.024 m in thickness needs to be considered to attain an accuracy of better than 90%. Photons with a frequency lower than 2 × 1015 Hz (150 nm in wavelength) can travel a considerable distance (>0.02 m) with an intensity attenuation factor of 0.2–0.8. Above 2 × 1015 Hz, only photons from the continuum spectrum can travel up to 0.015 m and line emission is absorbed within a distance of typically 0.0005 m, i.e. the arcing gas is optically thick to these photons. The gas within a cross-section of the arc column can be divided into a net emission core and a net absorption zone. The 55%–75% of the radiation emitted from the core is reabsorbed. The starting position of the net absorption zone sits within the temperature interval of 75%–80% of the maximum temperature on the axis. The quantitative information from this work is expected to serve as baseline data for developing improved approximate models for radiation transfer calculation in SF6 switching arcs.