Synthetic Tests of Capacitive Current Switching Using a Test Vessel

According to the relevant IEC standards vacuum circuit-breakers have to meet various needs, e.g. the interruption capability, making operations, and dielectric strength. Switching of capacitor banks, overhead lines, or cables leads to very small currents in comparison with short-circuit currents. After current interruption the circuit-breaker must withstand twice the peak value of the system voltage. Furthermore, restrikes can lead to voltage multiplication. The conjunction of relatively small breaking currents with high voltage stress must be considered in detail. This work introduces a test arrangement for combined tests of making operation, current interruption, and dielectric stress of a vacuum gap under capacitive switching condition. A test vessel permits investigations of various contact materials and designs. It is connected to a synthetic test circuit which provides the appropriate test currents and capacitive voltage. Both the appearance of pre-ignitions at contact closing and the behavior under capacitive voltage stress after breaking are observed as indications of the contact surface conditions