Vacuum interruption technology is the leading technology for the medium voltage range up to 52kV especially in the distribution circuits. Over the decades, the interrupting capability of the Vacuum Circuit Breakers (VCB) has increased significantly and their application range is extended even to generator circuits which are more demanding than the regular distribution breakers. With the recent developments, it is now possible to apply Vacuum Generator Circuit Breakers (VGCB) for the protection & synchronization of power plants rated up to 400MW. The generator circuits are particularly more demanding due to their high short circuit currents, high rated currents, delayed current zeros and very fast RRRVs and the vacuum interrupters have been proven to handle such stresses reliably. All the VGCBs must be tested according to the standard IEEE C37.013 which is created specially to address the above mentioned conditions. No emission of green house gases, easy to install, maintenance free, high number of short circuit interruptions and cost effectiveness are some of the distinctive advantages of the VGCB which are making it as a best alternative for another technologies for the generator circuit applications. Over the years, they are proved to be an economical and efficient solution in protecting the generators and step up transformers thus improving the plant efficiency and reliability. In contrary to many arguments against vacuum circuit breakers as generator circuit breakers, the vacuum interrupters too have an arc voltage up to 150V depending on the type of the contact which helps in damping the dc component and reduces the arcing time at-least up to two cycles or more. This paper gives a brief overview of the switching characteristics of the VGCB along with case studies that shows the influence of arc voltage in advancing the current zeros of a generator fed fault. Commercial simulation software called PSS NETOMAC is used to analyze the effect of arc voltage and the results are presented.
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