Performance evaluation of solid state fault current limiters in electric distribution system

The expansion of electric distribution system has resulted in an increasing need of fault current limiter in so as to limit fault currents to the downstream protection devices as a means of improving power quality. Considerations in the use of fault current limiter are that it must be reliable in operation, compact and inexpensive. This paper presents a comprehensive performance evaluation on the use of solid-state fault current limiters (FCL) in a distribution system. The FCL simulation model has been developed using the electromagnetic transient program PSCAD/EMTDC and a new control strategy for the FCL has been proposed for instantaneous detection of over current. The FCL is evaluated in terms of its performance in limiting fault current to the tolerable limit of the system, as well as the response of the FCL within a fraction of a cycle of about 2 ms. The effects of varying circuit parameters such as R, L, and C as part of the FCL device has been investigated. It has been noted that the inductive reactor, which is part of the FCL device, is suitable for limiting the fault current. The impact of induction motor loads on the FCL has also been analyzed. Simulation results show that the FCL is effective for reducing short circuit currents and also can be used to protect bus bars from voltage sag when the system is subjected to various types of faults.