Deformation of contact surfaces in a vacuum interrupter after high-current interruptions

The molten contact surfaces, which are caused by interrupting high currents in a vacuum interrupter (VI), can be induced to form Taylor cones by electrostatic force after current zero. Moreover, the deformation caused by the Taylor cones can further enhance the local electric field at their tips, which lead to breakdowns during post-arc phases, and make the interruptions fail. The objective of this paper is to simulate how the Taylor cones are brought out, considering influences of initial shapes, electric fields. An electrohydrodynamic (EHD) model was adopted, and the interface between vacuum and liquid metal region was traced by the level-set method. The results show that the presence of a protuberance indeed can transform to a local field enhancing Taylor cone if the liquid metal surface is exposed to a large enough electric field. Besides, the threshold for Taylor cone formation decreases when temperature of electrode increases. Consequently, the possibility of breakdown in a VI after high-current interruptions increases as well.