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The Vacuum Arc
Published in Paul G. Slade, The Vacuum Interrupter, 2020
All arcs that initiate between opening contacts form in metal vapor from the molten metal bridge and are thus metallic arcs. They all eventually transition into arcs that operate in the ambient atmosphere surrounding the contacts. Thus, a contact opening in air will transition from an arc burning in metal vapor to one burning in air [22]. Similarly, an arc burning between contacts opening in SF6 will transition to an SF6 arc. In vacuum, the “vacuum arc” continues to be a metal vapor arc, i.e., the only gaseous medium available in which the arc can operate is that evaporated from the contacts themselves. I will discuss three types of vacuum arc:The diffuse vacuum arc for currents ≤ ~ 6kAThe columnar vacuum arc for currents ≥ ~ 10kAThe transition vacuum for currents ≥ ~ 6kA ≤ ~ 10kA
Circuit Breakers
Published in Martinez-Velasco Juan A., Power System Transients, 2017
Juan A. Martinez-Velasco, Marjan Popov
There is no mechanical way to cool a vacuum arc, and the only possibility to influence the arc channel is by means of a magnetic field. The vacuum arc is the result of a metal-vapor/ion/electron emission phenomenon. To avoid uneven erosion of the surface of the arcing contacts (especially the surface of the cathode), the arc should be kept diffused or in a spiral motion; this can be achieved by making slits in the arcing contacts or by applying horseshoe magnets. The movement of the circuit breaker moving contacts is achieved by means of steel bellows (see Figure 7.25).
Current distribution reconstruction in switching arcs by means of regularization based on GSVD
Published in Inverse Problems in Science and Engineering, 2021
Hongchen Zhao, Xiaoming Liu, Hai Chen, Peiyuan Li
In switchgear with contacts, vacuum circuit breakers (VCBs) inevitably ignite arcs during the switching process. The current density distribution of the arc is one of the factors that determine the spatial variation of the heat flux, the temperature of the metal vapour vacuum arc, and the rate of electrode erosion in the vacuum interrupter. At present, investigative approaches to the switching arc consist of combinations of experimental and numerical analysis. Experimental approaches make use of charge- coupled device (CCD) cameras, optical fibre arrays, spectrum analysis, and magnetic diagnostics. The first three methods use optical testing and require drilling holes in the interrupter walls or the use of transparent wall materials to observe the dynamic arc characteristics. These optical methods are intrusive as the modifications affect the physical properties and pressure distribution in the interrupter.