Optimization based control of overcurrent relays in distribution network considering real-time measurements: A case study

The coordination time interval (CTI) is very important in the coordination of overcurrent relays (OCRs). Although the CTI constraint is usually taken as 0.2 in the literature, it is also stated that it can be taken at different values. In the relay coordination carried out on a real power system serving in Erzurum/Turkey, the triping delay times (TDT) of OCRs and the contact opening delay times (CODT) of circuit breakers (CB) were measured and the CTI constraints in the coordination were determined according to the obtained measurements. This coordination process was transformed into an objective function (OF). This OF was solved with metaheuristic optimization algorithms. The Dandelion Optimization (DO) solution is better than spider wasp, golden jackal, zebra and dingo based optimization. Then, time multiplier setting (TMS) values are obtained from OF according to the CTI value determined according to the proposed real-time measurement and the CTI = 0.2 value frequently preferred in the literature. The performance of the relay TMS values obtained according to the proposed and classical methods was compared. Considering the power model and solution, 18.67 % improvement in the operation times of the relays was achieved in Relay 2, 11.67 % in Relay 3, 19.94 % in Relay 4, 28.6 % in Relay 6 and 23.31 % in Relay 7. The TMS value of Relay 5 is the same for the proposed and the classical method. As a result, the fast operation, reliability and selectivity of the power system were improved by ensuring correct relay coordination with the proposed method.