Specification of fault current limitation level for FCLs in power systems

With the increasing capacity of power system, fault currents (CBs) may exceed the interrupting capacity ratings of circuit breakers. Fault current limiters (FCLs) can be applied to maintain circuit breakers within their interrupt ratings. The degree of fault current limiting on system performance is analyzed in radial and meshed system structures. Heavy limitation modes and light limitation modes are defined. The choice of limitation mode should be based on the locations of FCLs. We discovered that FCLs should work in light limitation mode to maintain the function of circuit breakers in a radial structure, or a matrix structure with changeable relay schemes, but that FCLs should work in heavy limitation mode in a matrix structure with unchangeable relay schemes, to limit the fault current contribution from newly-added distributed generators. The analyses are verified by simulation results.