Vacuum Breakdown between Molten Metal Electrodes

The presence of molten metal on the surface of the electrodes of vacuum circuit breakers, following the interruption of high currents, is a potential source of reduction of breakdown strength. The authors thus devised special experiments to study this effect by separating the roles of the presence of the metal vapour from that of the presence of a molten metal. The experiments also separate the pure dielectric effect from that of the post arc plasma sheath and its dynamic movement, under the influence of the transient recovery voltage, TRV. The results show clearly the large reduction of breakdown voltage which can occur in under these circumstances. These results allow an improved understanding of the physical mechanisms taking place under the transient plasma sheath during the TRV