Finding Optimal Zone II Settings for Distance Relays in Coordination With Directional Overcurrent Relays Using QCQP Algorithm

This paper introduces a deterministic method to address coordination challenges between distance relays (DS) and directional overcurrent relays (DOR) by employing quadratic programming with quadratic constraints (QCQP). The conventional nonlinear coordination problem associated with DORs is reformulated as a QCQP, incorporating quadratic constraints, and the zone-II setting of the DS relay is included as a variable. To optimize relay settings that adhere to coordination constraints, the approach eliminates redundant constraints, proposing a minimal coordination constraint set (MCS) to prevent miscoordination issues. Furthermore, the MCS is divided into subsets suited to specific network topologies, thereby reducing programming complexity and execution times. Implementing QCQP with MCS and the SCIP optimizer (a global optimization tool) led to significant reductions in operating times as 86.4%, 10.77%, and 72.4% for the 8-bus, 14-bus, and IEEE-39 bus system models, respectively. These results highlight the QCQP approach's superiority over previous solutions, demonstrating its effectiveness in optimizing power system protection operations while substantially reducing computation times compared to existing methods.