Method of Recloser-Fuse Coordination in a Power Distribution System With Superconducting Fault Current Limiter

In this paper, we analyzed recloser to fuse protective coordination when superconducting fault current limiters (SFCL) are applied into power distribution system. Generally, fuses are installed at more remote position from substation than reclosers. Thus, when instantaneous faults occur at the point behind the fuse, the fuse doesn´t melt because the recloser removes the fault by reclosing operation. When permanent faults occur, the fuse has to melt just before the last delay trip of the recloser in order to prevent the loads between the recloser and the fuse to be interrupted. However, in power distribution system with SFCL, the fault current is decreased by the effect of the impedance of the SFCL. In this case, when a permanent fault occurs, the fuse may not melt during the delay operation of the recloser because of the insufficient heat from the decreased current. As a result, the recloser is locked-out and the loads between the recloser and the fuse are interrupted unnecessarily. Therefore, when SFCLs are applied into power distribution system, the rating of fuse has to be reselected to coordinate recloser-fuse effectively. However, this reselection for the protective coordination becomes very complicated problem considering the impedances of generator, transformer, distribution line, fault and so on. To solve these problems, we proposed the method to calculate and select the ratings of fuse using the above-mentioned impedances. The proposed method will be proved through the case studies.