Growth of vacuum interrupter application in distribution switchgear

This paper reviews the continued development of vacuum interrupter technology. It presents an analysis of why the use of the vacuum interrupter in equipment developed to switch and protect distribution circuits continues to increase. Firstly, results from the high level of R and D investment in this product are discussed. This discussion focuses on three major subjects: (a) the advances in the application of vacuum technology, (b) the understanding and the control of the vacuum arc, and (c) the development of new materials. It is then shown how the continued development of the vacuum interrupter has benefited from this R and D: the improvement in vacuum interrupter design; the increase in its interrupting performance; the extension of its operating life and reliability; and a continued increase in its value (i.e. the continued decrease in cost for a given interruption rating). A discussion is presented on how these improvements in vacuum interrupter design have led to an ever broadening of its range of application. Finally, the future outlook for the application of the vacuum interrupter is discussed with special reference to low life cycle costs, the potential for maintenance free equipment, and the capability of continuously monitoring vacuum interrupter switching life.