Enhancing the performance of directional relay using a positive-sequence superimposed component

In this article, we propose a fault directional identification scheme that depends on the positive-sequence components of current based on an investigation of pre-fault and fault phase angles. The proposed protection scheme is developed for both distribution and transmission systems. However, as the current-only approach depends on the pre-fault current direction as the polarizing quantity, if the pre-fault current direction changes during normal conditions, the direction definitions would be swapped. This will cause a problem for the current-only approach. Therefore, a signal processing-based solution is presented, leveraging the fact that a change in direction in the pre-fault condition is associated with a phase angle change of 180°. The proposed protection scheme is examined with two different power system configurations (distribution and transmission systems). Simulation experiments conducted using ATP/EMTP software verified the feasibility of the proposed protection scheme. Moreover, the validity of the proposed protection scheme is compared with that of other directional schemes. The results confirmed the accurate operation of the proposed scheme.