Optimum Time Coordination of Directional Overcurrent Relays Using CVX, GAMS and Genetic Algorithm

This paper proposes new optimization techniques to obtain optimal values of Time Multiplier Setting (TMS) for directional overcurrent relays (DOCRs) in a protection scheme. General Algebraic Modelling System (GAMS) and CVX modelling system for convex optimization are the new techniques proposed. TMS of DOCRs needs to be accurately determined in order to coordinate the operating time and avert the mal-operation of the backup relays in the transmission and distribution network. Without optimum coordination of the action of relays, fault conditions will trip healthy transmission lines and might lead to a total shut down of the grid. The time coordination of relays in a network is an extremely constrained optimization function which identified as a linear programming problem (LPP). Of late, the use of genetic algorithm (GA) for DOCRs coordination have become increasingly prominent. Therefore, the proposed CVX and GAMS techniques are compared with conventional GA scheme. Results show that an accurate optimization solution for directional overcurrent relay coordination can be achieved using both GAMS and CVX methods in comparison to GA based method with GAMS providing a more accurate solution.