The Optimal Setting of Inverse Time Overcurrent Relay in Distribution Systems Installed with Smart Grounding Device

摘要

For distribution systems, transition resistances affect the fault current greatly, especially when the single phase to ground fault occurs. Since the fault currents varies with different values of transition resistances, it is suggested to utilize the inverse time overcurrent relays in protection process. For neutral point ineffective grounding systems, a smart grounding device is recently proposed to be installed. This device can add a small resistance to the neutral point and multiplies the fault current for easier protection. Under such circumstances, this paper utilizes the Exhaustive Search based method to obtain the optimal settings of the relays. The selectivity and the speed of the relays are demonstrated through a 10KV distribution system.