Sequence Current Components Based Directional Relaying Technique for Unsymmetrical Faults

The transmission line protection schemes should offer better reliability, sensitivity, selectivity, and stability and be economical with high operation speed. Directional relays play a vital role in protecting the transmission line. In this paper, a highly efficient current-based directional protection algorithm is introduced. The proposed technique does not use the pre-fault data, and only the post-fault current signal is utilized; hence, it can successfully work under CVT transients and close-in faults. In this technique, the ratio of negative to positive (RNP) sequence post-fault current phasor is defined for fault detection. The trajectory of the ratio outside the specified security region decides the occurrence of the fault, i.e., forward or reverse unsymmetrical faults. Simulation results are carried out considering the different values of fault resistance and fault location with various unsymmetrical faults. These simulation trials have been conducted using PSCAD and MATLAB 2019a software. The comparative analysis with previous similar proposed techniques is presented. Simulation results under various operating conditions confirm the effectiveness and accuracy of the proposed technique.