Application of current limiting fuses in distribution systems for improved power quality and protection

This paper presents a comparative analysis of the effects of distribution system expulsion and current limiting fuse operations on power quality. To perform this analysis, digital fuse models were developed for use with the EMTP/ATP program. Expulsion fuses interrupt current at current zeros and are easily modeled. Current limiting fuses (CLFs) interrupt current by forcing a current zero and therefore, require a special modeling technique. CLFs were modeled by representing them as nonlinear resistances. The nonlinear resistances were calculated using laboratory test results of actual CLF operations. This technique is very convenient for simulating CLF operations and analyzing their interaction with the distribution system. This paper shows that CLFs improve power quality by supporting system voltage during faults and reducing voltage dip duration. Additionally, CLFs reduce the fault let-through I/sup 2/t.