Optimal Coordination of Overcurrent Relays using Gravitational Search Algorithm with DG Penetration

Modern distribution systems consist of various distributed generators (DG) to make reliable power systems. In these DG integrated distribution systems, coordination of overcurrent relays is a big challenge for protection engineers. With the addition of DG, distribution system experiences change in the short-circuit level of the system and thus earlier relay settings causes mal operation of relays. Nowadays, various programming optimization techniques are frequently used to find optimal relay settings of overcurrent relays. This paper presents a comparative study of particle swarm optimization and Gravitational Search Algorithm for the coordination of overcurrent relay for a system containing DG. A proper combination of primary and backup relay is selected to avoid mal operation of relays and unwanted outages when DG is penetrated. Practical cases with different DG penetration level and fault types are also thoroughly discussed. A 4-bus radial system is simulated in PSCAD/Simulink platform and programming is done using MATLAB software.