Interruption performance at frequency 50 or 60Hz for generator breaker equipped with vacuum interrupters

Vacuum interrupters are serving worldwide in distribution circuits, meeting the electrical and mechanical requirements specified in the IEC and/or ANSI standards for low and medium voltage applications. Generator circuits require special generator circuit-breakers and are tested according to IEC 62271-37.013/ANSI/IEEE C37.013. Traditionally, generator circuit-breakers have been very large devices based on air- or SF6- blast interruption technology. Over the last 35 years, the short circuit interruption performance of vacuum interrupters has been dramatically increased due to continuous development, especially of contact system design and contact materials. These improvements allow the application of vacuum interrupter technology to generator circuit-breakers. Three phase vacuum circuit-breakers are available for this application in generator circuits at 50 and 60 Hz. To fulfil the required short circuit interruption ability, the test has to be performed at 50Hz for IEC markets and at 60Hz / 50Hz for ANSI markets. When the short circuit interruption ability is tested at 50Hz, the results can be transferred to 60Hz because the arcing time is reduced, while the di/dt is slightly steeper at current zero. Four main factors related to vacuum technology are investigated: The influence of the arcing time duration before current zero (CZ), the transferred charge I x dt, di/dt steepness at CZ, and finally the transient recovery voltage (TRV).