The Coordination Time Interval Constraint Does Not Guarantee Optimal Overcurrent Relays Coordination

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Almodafer A. A., Gökalp E., Ateş Y.

10th international congress on engineering architecture and design, İstanbul, Turkey, 24 - 26 December 2022, vol.76, no.16, pp.1351-1362

  • Publication Type: Conference Paper / Full Text
  • Volume: 76
  • City: İstanbul
  • Country: Turkey
  • Page Numbers: pp.1351-1362
  • Yıldız Technical University Affiliated: Yes


This study seeks to verify the veracity of the concepts utilized in most of the published articles on optimum overcurrent relays' (OCR) coordination, namely, the assumption that the objective function (the lowest sum of operating times for the primary overcurrent relays) and its constraint of maintaining the numerical value of the coordination time interval (CTI) ensure the validity of OCRs' coordination in optimization algorithms. Since most distribution stations in Iraq are similar, the Hemdan 33/11 kV substation (2 x 31.5 MVA) in Basra, south of Iraq, was chosen as a model by considering the connection of three distribution generators (DG) to different locations of the network. We took into account the topological change caused by the variation in the operational state of the DGs (Turn-off and Turn-on). After conducting a comparative study between the genetic algorithm (GA) and the biogeography-based optimization (BBO) in the MATLAB platform, this study proves that the CTI constraint is not a guarantee of the coordination accuracy and that the lower the value of objective function, the worse the OCRs' coordination becomes. It also proposes an adaptive mechanism for coordinating OCRs due to changing the operational status of the DG's connected to different sites of the network using the GA.