Increase in power generation capacity of electric power systems has lead to
increase in the fault current level. In some cases fault current levels are exceeding the
interrupting capability of existing transmission and distribution substations circuit
breakers. Since short-circuit currents contain extremely high energy and can damage
electrical equipment, either requires the replacement of a large number of existing
substation breakers with higher rating breakers or the development of some means to
limit fault current. Different technologies have been employed to design Fault Current
Limiters FCLs such as turn-off a solid state switch to using superconductors that
respond with increasing resistance in event of fault current. A proper design of
Modular Level Based Solid-State Fault Current Limiters is proposed in this paper,
describes the functioning of FCL and the amount of impedance they are required to
insert in series with transmission or distribution substation are discuses. This will
allow near instantaneous breaking of bus ties in transmission and distribution
substations to reduce the available short circuit current and allow existing circuit
breakers to clear at lower fault current levels. Since FCL's are installed in each phase
of the line, the fault is viewed in perspective of per phase. For the purposes of this
study, we consider phase to ground fault& phase to phase fault scenarios.