The purpose of this study was to analyze
instability of silver and palladium as alloy cathode on the contact surface in a vacuum and make comparison. We
also focused on new alloy materials, mainly Pd, a material with low ionization tendency. We observed unstable current chopping phenomenon when Ag and Pd were used in a vacuum circuit breaker to evaluate the unstable region. So far, we changed the percentage of materials in a
compound electrode material of Ag and Pd to 1 %, 2 %, and 4 % to observe the changes in the transient voltage as the percentage of Pd on the cathode spot increased. We also performed simulation using bisection method to evaluate the degree of ionization in the collisionless sheath. In the cathode spot region, these collisions are recognized as space charges and sheaths when connected to a single ionization collisional plasma. In the preceding works, we found out that the transient voltage dropped when the
percentage of Pd in the cathode increased. Main operating principle of the vacuum circuit breaker used in a switchgear is to have electrodes in high vacuum and when the arc discharge generated upon opening of the electrodes
becomes metallic vapor which will be ionized between electrodes and maintain the arc discharge, and then becomes an excellent insulator to shut off the transient
current.
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