A SPECTROSCOPIC INVESTIGATION OF ELECTRODE MATERIAL ENTRAINED INTO THE EXTINGUISHING ARC OF AN SF6 CIRCUIT-BREAKER

Spectra of SF6 circuit breaker arcs during the arc extinction phase following peak currents up to 53 kA have been obtained in the wavelength range 510-517 nm. Copper emission lines and irregularly occurring tungsten emission lines from entrained contact material have been identified and the ratio of the number density of tungsten to copper atoms estimated from the line intensities. An approximate radial distribution of both copper and tungsten line intensities has also been obtained. An approximate correlation is shown to exist between the occurrence of tungsten line emission at the critical instant of current zero when current interruption is sought and a sharp deterioration in the current interrupting ability of the circuit breaker.