A Novel Scheme for Current Only Directional Overcurrent Protection Based on Post-Fault Current Phasor Estimation

A reference voltage phasor plays an important role in traditional directional overcurrent relays, which need current and voltage measurement to detect fault direction leading to additional cost. The present study aimed to introduce a novel current-only directional detection possibility scheme, which can detect the fault direction by using only the post-fault current. To this aim, a new reference phasor was introduced to detect the fault direction, which was constructed from post-fault current by using S-Transform. Thus, this procedure is not complicated without any potential transformer. The proposed scheme was demonstrated by using algebraic formulation. In order to verify the method, it was implemented in Matlab/Simulink for different conditions of faults. The results demonstrated that the proposed scheme could detect the direction of faults precisely and could be used in the smart grid systems.