Influence of contact erosion on the state of SF6 gas in interrupter chambers of HV SF6 circuit breakers

A considerable part of the energy released by electric arc during breaking of a short-circuit current is being absorbed in the moving and stationary arcing contacts. The rest of the energy is being released as thermal stresses of the nozzle and of other parts of the arcing chamber, as well as heating, dissociation and ionization of the arc extinction medium, and in losses to the nearby environment. The absorption of the energy causes heating, melting and finally the vaporization of contact material and it is the main cause of contact erosion. It is obvious that the process of arcing contact erosion has a considerable influence on the state of SF6 gas in the contact gap, but also in the adjacent interrupting chambers. A contact erosion model is incorporated into a computer program for high voltage circuit breaker interruption simulation. The calculated contact erosion intensity is verified by comparing the calculated change in the contact shape and mass losses with experimentally obtained data. The influence of vaporized contact material on the state of SF6 gas in the interrupter chambers and the dielectric performance of the contact gap is also analyzed and discussed.