Controlling breakdown charge for conditioning procedure in vacuum under non-uniform electric field

Summary

In order to improve the dielectric strength of vacuum circuit breakers, it is important to grasp the characteristics of spark conditioning in vacuum. In this paper, we discuss the optimum conditioning procedure in vacuum under non-uniform electric field in terms of breakdown charge during the conditioning procedure, which can be expected to satisfy both higher saturated breakdown voltage and the efficient conditioning procedure. We set a rod-plane electrode configuration with the gap distance of 2 mm and the tip radius of the rod electrode of 2 mm. We applied negative lightning impulse voltages to the rod-plane electrode system for the spark conditioning of electrodes in accordance with up-down method. We controlled the discharge current at breakdown during the conditioning procedure by changing the limiting resistance of the impulse generator, in other words, the primary conditioning with the large breakdown charge was followed by the subsequent conditioning with the suppressed breakdown charge. As a result, when we carried out the primary conditioning with the relatively small breakdown charge without a large damage on the electrode surface, we could obtain the preferable conditioning effect of the subsequent conditioning with the moderate breakdown charge, which emerged as the improvement of the minimum breakdown voltage while maintaining the high saturated breakdown voltage. On the other hand, when we carried out the primary conditioning with the excessive breakdown charge with a large damage on the electrode surface, though the conditioning reached the earlier saturation, the minimum breakdown voltage was not improved even after the subsequent conditioning was saturated. This is because the damage on the electrode surface was not enough recovered in the subsequent conditioning with the moderate breakdown charge.

Additional informations

Authors

DE MORAES AMANCIO, DE MELO ALVES, GERMANO, Pozzati

Keywords

vacuum circuit breakers, vacuum interrupters, vacuum discharge, conditioning procedure, breakdown charge