Use of genetic algorithms (GA) for optimal coordination of directional over current relays

In this paper, the optimization of coordination of directional overcurrent relays in an interconnected power system is presented. The objective of protective relay coordination is to achieve selectivity without sacrificing sensitivity and quick fault clearance time. A methodology is adopted for the consideration of backup relays in the optimal coordination of directional overcurrent relays. The calculation of the time dial setting (TDS) and the pickup current (Ip) setting of the relays is the core of the coordination study. The inequality constraints guarantee the coordination margin for each primary/backup relay pair having a fault very close to the primary relay. Using this formulation, the size of the optimization problem is significantly reduced. Genetic algorithm is the algorithm being applied to minimize the operating times of the relays. In this paper both linear and non linear equations are framed for the 8 bus test system used and optimized using the genetic algorithm.