Spectroscopic Investigation of Metal Content in Prestrike Arc During Making Operation in a Low-Current Model Switch

Energy dissipation during prestrike arc is the critical factor for electrical contacts erosion and welding in medium voltage load break switches. Using air-filled devices as an alternative to SF6 makes the switch environmentally friendly, but leads to a more challenging process due to a higher prestrike arcing time between contacts. Therefore, understanding the erosion process of electrical contacts is crucial to improve the switch lifetime. Determination of contacts surface evaporation by optical emission spectroscopy is one of the most precise methods to investigate the prestrike arc interface with the contacts. In this article, the temporal and spatial profiles of copper and tungsten emitted species during prestrike arc are presented. For this purpose, a circuit consisting of a synthetic dc high voltage part is used to initiate the arc. The temporal evolution of CuI, CuII, and WI shows evaporation of the cathode and the anode surfaces during the prestrike arc, and the spatial profiles show an inhomogeneous distribution of the vapors alongside the arc root.