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Microparticles are an inevitable component of vacuum arcs. This paper focused on the dynamics of microparticle and erosion behavior in high-current vacuum arcs. The arc was sustained with AC 110 Hz between two butt CuCr alloy contacts with a diameter of 10 mm. An in situ microparticle diagnostic system suitable for vacuum arcs was developed. Three sources of microparticles were observed and the corresponding motion characteristics were obtained by our method. The influence of current and Cr content on erosion characteristics was investigated. The results indicate that the increase of Cr content contributes to inhibiting production of microparticles when the current is small. CuCr30 has the best effect of suppressing microparticle production among the three tested alloy materials under large current. The work of this paper helps with the understanding of microparticle behavior in high-current vacuum arcs and may provide a path for the design of a vacuum electrode.

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.

Arc discharge in water can generate extremely high voltage, which has great potentials to be used in DC fault protection. The voltage characteristic is closely related to the arc behaviors. However, due to the complexity of the gas-liquid mixed environment, the arc shape is difficult to be observed directly. In this letter, an observation device is specially designed and underwater arc motion with millisecond-scale duration is clearly photographed. The corresponding relationship between arc behaviors and its varied voltage is revealed. Besides, the random behaviors of underwater arc is controlled stably by applying external transverse magnetic field (ETMF). The enhanced cooling mechanism and the directional arc motion characteristics are discussed. It demonstrates that, fast elongation of arc column and continuous heat exchange between phase surfaces are the keys to realize rapid increase of underwater arc voltage.