Fault Current Limiter: An Enabler for Increasing Safety and Power Quality of Distribution Networks

The impact of fault current limiter (FCL) devices on safety and power quality of distribution networks is quantitatively investigated. The thermal let-through caused by actual short-circuit current waveforms rather than the rms value of the symmetric component is introduced to assess the impact of the fault. Situations of vulnerability caused by a very high short-circuit current for distribution networks supplied by large power transformers, especially if operating at a lower voltage, are discussed. Concerning power quality, the possibility of restricting, by means of an FCL, the area affected by voltage dips due to a polyphase fault, thus avoiding the propagation of the disturbance to all customers, is investigated. The impact of the FCL on dispersed generation (DG) is also looked into. In particular, the possible use of FCL for avoiding unwanted trips of protection due to the DG is discussed. Finally, the possibility of interconnecting, by means of an FCL, two distribution networks without risking excessive vulnerability in the event of a fault is discussed, and the increased performance of such interconnected networks in terms of maximum permissible disturbing power is quantitatively assessed.