Protection of large D-C machines by means of high-speed circuit breakers

THE problems of protecting large installations of rotating d-c machines have been neglected to some extent by the lack of suitable high-speed switchgear rugged enough to stand the severe duty usually encountered. The authors are describing their analysis of probable short-circuit characteristics of such large systems and a high-speed breaker rated at 7,500 amperes which has been developed for this particular purpose. The authors are also describing a large rotary-converter installation built some time ago which has recently been modernized by means of modern switchgear in order to overcome the serious damage caused to the rotating machines resulting from the inadequacy of the originally installed switchgear.