The influence of the contact materials arc-conditioning method on electric strength of vacuum interrupters stored in nonvoltage state

The electric strength between open contacts of a vacuum interrupter must fulfil the requirements of adequate IEC standards. For a long vacuum gap (10-14 mm) there is a strong relation between breakdown voltage U_b and charge Q_max as well as microdischarge onset voltage U_MD. These chosen parameters can be treated as very good criteria of electric strength of a vacuum gap. In this paper the authors compared the electric strength degradation of chambers prepared with various arc conditioning processes. The test objects were commercially made medium voltage (12 and 24 kV) extinguishing chambers of a vacuum interrupter with CuCr sintered contacts