Optimal Coordination of OCR with TCC Selection for Radial Industrial System Using Firefly Algorithm

Overcurrent relay (OCR) is the primary protection in the distribution system. The advantages of OCR in the protection system is the ability to work coordinately in time, current, time-current grading. To attain the coordination setting of OCR, it requires a proper minimum operating time (TOP) and satisfied coordination time interval (CTI). However, attaining the coordination of OCR is quite challenging when distributed generations (DGs) are presented in the power system. The presence of DGs gives additional fault current contribution to the fault location. In this paper, Firefly Algorithm (FA) is proposed to solve the coordination of OCR. The FA will be used to obtain the time dial setting (TDS) with an objective to minimize the TOP and constraint of satisfying CTI for all possible network topologies and DGs operation. The proposed method is tested in a radial distribution system with active DGs of a real industrial petrochemical plant. The result of FA optimization is compared in different curve characteristics according to the IEC Standard 60255.