Impact of distributed generation on coordination of overcurrent relays in a benchmark distribution system

The process of defining settings among various protective devices such that these devices operate in a specified order on the occurrence of any undesired fault in the system is known as protection coordination. This paper presents an analysis of coordination among various overcurrent relays (OCRs) in a benchmark system with the connection of distributed generators (DGs) at different locations. In the first case only one DG is integrated to the distribution system and the coordination characteristics has been calculated for various overcurrent relays in the system. Whereas in the second case two DG is connected at suitable locations to find out the coordination characteristics of OCRs installed in the distribution system. The objective function (OF), which is a function of time multiplier setting (TMS), is formulated for each case. The prime objective of this paper is to demonstrate a comparative study of protection coordination among various OCRs using different optimization techniques. In this paper genetic algorithm (GA), particle swarm optimization (PSO) and gravitational search algorithm (GSA) has been used for the optimization of TMS and total operating time of the relays. All the studies have been performed on IEEE-34 node benchmark distribution system which is simulated in MATLAB.