Overcurrent Relays Coordination of Interconnected Power System using Modified Objective Functions and Multiple Standardized Tripping Curves

Over the last few decades, many researchers opt various techniques to achieve optimum time for coordination of overcurrent relays. The main motive of these techniques is to avoid mal operation among the main and secondary relays and to reduce time of operation of each relay as per required criteria. Some researchers have suggested modification in relay characteristics and objective functions to avoid mis-coordination. Three objective functions from the literature are examined in this paper, and new modified objective functions are the suggested after modification. A comparison is made between the standard objective function with modified obje ctive functions. Out of three modified objective functions, the best modified objective function is proposed. Further, three IEC standard relay characteristics have been adopted to analyze & compare the effectiveness & robustness of said objective functions. For the said comparison IEEE 14-bus modified distribution system is considered and a Harmony search algorithm is used.