Fault direction identification utilizing new current-based index founded on rate of change of fault current

Abstract The proliferation of Distributed Generations (DGs) in distribution networks has provided power system operation improvement while raising some protection challenges. Turning to bi-directional, the protection schemes of the deregulated distribution networks should be able to deal with an out-of-zone fault. More specifically, DGs impose bi-directional fault current and directional relay should be employed to identify correct fault direction so that the protective relays are prevented from mal-operation of out-of-zone fault. This paper introduces a current-based directional algorithm that utilizes a pre-fault current signal as the reference. This algorithm is designed based on the pre-fault current and rate of change of the fault current. As it can be inferred from the mathematical basis of the proposed method, it has low sensitivity to decaying DC and noise components. Also, the proposed index has a certain and straightforward range of variation between (-1, 1) for backward and forward fault direction, respectively. The performance of the proposed algorithm is evaluated for different scenarios such as variation of fault resistance, sampling frequency, and types of faults in three simulated systems and a laboratory test bench. The simulation and experimental evaluation results show the accuracy and speed of the proposed algorithm in comparison with similar algorithms.