The splashing erosion of electrodes in a DC atmospheric-pressure air arc has been investigated by visualization of the electrode surface and the sputtered droplets, and tracking of the droplet trajectories, using image processing techniques. A particle tracking velocimetry algorithm has been introduced to measure the sputtering velocity distribution. Erosion of both tungsten–copper and tungsten–ceria electrodes is studied; in both cases electrode erosion is found to be dominated by droplet splashing rather than metal evaporation. Erosion is directly influenced by both melting and the formation of plasma jets, and can be reduced by the tuning of the plasma jet and electrode material. The results provide an understanding of the mechanisms that lead to the long lifetime of tungsten–copper electrodes, and may provide a path for the design of the electrode system subjected to electric arc to minimize erosion.

In this paper, the radial temperature distributions of the blown CO 2 arcs in a model gas circuit breaker were investigated by optical emission spectroscopy methods. The CO 2 flows with different flow rates (50, 100 and 150 l min −1 ) were created to axially blow the arcs burning in a polymethyl methacrylate (PMMA) nozzle. Discharges with different arc currents (200 and 400 A) were conducted in the experiment. The absolute intensity method was applied for a carbon ionic line of 657.8 nm to obtain the radial temperature profiles of the arc columns at a cross-section 1 mm above the nozzle. The calibration for the intensity of the C II 657.8 nm line was achieved by the Fowler-Milne method with the help of an oxygen atomic line of 777.2 nm. The highest temperature obtained in the arc center was up to 19 900 K when the arc current was 400 A and the CO 2 flow rate was 50 l min −1 , while the lowest temperature in the arc center was about 15 900 K when the arc current was 200 A and the CO 2 flow rate was 150 l min −1 . The results indicate that as the arc current increases, the temperature in the arc center would also increase apparently, and a larger gas flow rate would lead to a lower central temperature in general. It can also be found that the influence of the CO 2 flow rate on the arc temperature was much less than that of the arc current under the present experimental conditions. In addition, higher temperature in the arc center would cause a sharper temperature decrease from the central region towards the edge.

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Carbon dioxide (CO) is a promising alternative to sulfur hexafluoride for high-voltage circuit breaker applications. It is important to have a detailed understanding of CO arc properties. In this paper, radial temperature distribution of the free burning direct current arc in pure CO was investigated. Optical emission spectrometry was applied under different pressures (0.5 atm, 1 atm, and 1.5 atm) and at different axial positions (1 mm, 2 mm, 3 mm above the cathode). Assuming local thermodynamic equilibrium, the Fowler-Milne method was adopted for O I 715.67 nm and O I 777.19 nm in the periphery of the arc, and the single-line method was adopted for C II 657.81 nm near the center of the arc. Radial temperature profiles obtained by these two methods were combined at the position where normal temperature was assigned. The results indicate that near the center of the arc, higher pressure would lead to lower temperature; as the distance from the cathode to the position measured increases, the maximum temperature in the arc center would decrease. In addition, the temperature would decrease more sharply toward the periphery if the central temperature of the arc is higher.