Current-only Directional Overcurrent Protection Using Postfault Current

Directional overcurrent relays play an important role in protecting the transmission and distribution systems. Conventionally, voltage profile is utilized as a polarizing reference quantity for the directional protection. During the close-in-faults, the conventional relaying technique loses its voltage reference signal. Moreover, the implementation cost of the method increases in distribution systems as it requires installation of potential transformers. In this paper, a novel method for identification of fault direction is proposed that only requires postfault current signal and does not require voltage signal. According to the case study results, the proposed method can determine the direction of faults precisely even in the case of change in the prefault power flow direction.