Moving from withdrawable to fixed circuit breaker switchgear in ANSI medium voltage applications

In the United States, medium-voltage power distribution typically uses withdrawable circuit breaker switchgear. Withdrawable breakers allow for regular maintenance and provide an easily visible confirmation of circuit isolation but at a cost — having removable parts and the act of inserting and withdrawing breakers could result in the possibility of causing arc flash incidents. Modern fixed circuit breaker switchgear, which uses highly reliable and virtually maintenance-free vacuum and gas breakers, eliminates this concern and introduces other potential advantages. This paper contrasts the features of medium-voltage fixed circuit breaker switchgear and existing withdrawable circuit breaker switchgear designs. Modern fixed circuit breaker switchgear design elements that are discussed include an internal disconnect for isolation and grounding of circuits; and interlocked operation among disconnect, breaker, and grounding switch for improved safety. Furthermore, features such as lower maintenance, smaller footprint, and reduced life-cycle costs that result from its simpler design will be explored. By comparing the traditional ANSI withdrawable circuit breaker switchgear technology to that of the fixed circuit breaker switchgear, this paper will demonstrate that the fixed design, which has gained widespread acceptance in global markets outside the United States, is a viable alternative to the withdrawable designs.