Spectral and spatial characteristic behaviour of three-dimensional radiation transfer in SF<sub>6</sub> switching arcs
S. Esmaeili, Petr Kloc, Jiu Dun Yan
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 SF 6 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 × 10 15 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 × 10 15 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 SF 6 switching arcs.