Optimal design and analysis of a variable reactor fault current limiter

Abstract

Development of power networks increases short circuit level and makes use of fault current limiters (FCLs) inevitably. FCLs should have low impedance in the normal condition of the network and high impedance quickly after the short circuit. For this purpose, a variable reactor has been proposed. In this scheme, the reactor impedance is dependent on the reactor air gap. In the normal condition, the reactor has a large air gap and has low impedance. When a fault occurs and the current increases immediately, a strong force is produced between the fixed and moving parts of the reactor and the air gap is decreased. This leads automatically to an increase in the reactor impedance. After the fault is cleaned, the reactor returns to its previous state by a spring and is recovered easily. An optimal design has been performed here to reach the FCL with desirable performance. To this end, analytical relations of the reactor are implemented and the optimum values are calculated by using genetic algorithm. The designed reactor has been simulated by the finite-element method to verify the analytical calculations. The results confirm the proposed scheme and indicate that the reactor limits the fault current very well.