Adaptive Protection Algorithm Considering N-1 Contingency Situation Using Setting Groups of Directional Overcurrent Relays

Conventional power systems are protected from faults by directional overcurrent relays with fixed setting values. However, if a power line trips or if distributed generation is disconnected due to a fault or maintenance, it alters the topology of the power system. Consequently, the magnitude of the fault current also shifts, potentially causing a breakdown in the protection coordination system. It is considerably difficult to protect the power system using fixed setting values. Therefore, this paper proposes an adaptive protection algorithm using the setting groups (SGs) of a numerical protection relay. The number of SGs that a numerical protection relay can contain is limited and less than the number of possible topologies of the power system. The proposed algorithm optimizes not only the setting values of each protective relay but also the combinations of SGs corresponding to each topology. This broadens the searching area for the optimization algorithm, aiding in effectively reducing the operation time of protective relays. The protection algorithm is verified using a modified IEEE 30 bus test system.