Limitations of fault-current limiters for expansion of electrical distribution systems

Application of fault current limiters (FCL's) has been recommended in the existing literature to retain underrated medium-voltage circuit breakers of lower short-circuit ratings in service, when the distribution systems are expanded and the short-circuit currents increase. However, the existing published literature does not describe the limitations of FCL's from system separation and loss of protective device coordination conditions, nor does it provide an analysis of short-circuit duties of medium-voltage circuit breakers used with FCL's. This paper shows how these evaluations can be carried out. Considerations of the high cost of replacements and the far greater loss of production, due to lack of coordination and availability of a proven alternate solution, should be included in an informed decision to use FCL's.