Optimum fault current limiter placement with search space reduction technique

A fault occurring in power networks normally results in a large short-circuit current flow in the system, which may exceed the rating of existing circuit breakers and can damage system equipments. Because of difficulty in power network reinforcement and the interconnection of more distributed generations, fault current level has become a serious problem in transmission and distribution system operations. The utilisation of fault current limiters (FCLs) in power systems could provide an effective way to suppress fault currents. In a loop transmission or distribution system, the advantages would greatly depend on the number and locations of FCL installations. The authors propose a method to determine the optimum number and locations for FCL placement in terms of installing smallest FCLs circuit parameters to restrain short-circuit currents under circuit breakers' interrupting ratings. In the proposed approach, the sensitivity factor, defined as the reduction of bus fault currents because of a given variation in the branch parameter, is derived and used to choose better candidates for active FCL installations. The search space for FCL installations can be reduced by using the proposed sensitivity factor calculation; therefore the computational efficiency and accuracy can be improved. A genetic-algorithm-based method is then designed to include the sensitivity information in searching for the best locations and parameters of FCLs. The test results demonstrate the efficiency and accuracy of the proposed method.