On 8-bus test system for solving challenges in relay coordination

The challenges in coordination of Overcurrent Relays (OCRs) are recognized as a nonlinear optimization problem with a large number of coordination constraints for multi-loop and multi-source interconnected networks. Several methods including topological analysis, deterministic and Artificial Intelligence (AI) based techniques are used to solve this problem. The 8-bus system is commonly used as a standard test case in majority of literature on relay coordination. This test case is employed in two ways: (1) 8-bus system without any link to another network and (2) 8-bus system with a link to another network, modelled by a short circuit power of 400 MVA. This paper presents simulation results of both the systems and demonstrates the results for researchers to test and validate their findings obtained using novel optimization algorithms and allied research. The various efforts to solve challenges in relay coordination are discussed with respect to the system and optimization algorithms. The paper concludes with an open ended discussion on selection of system, use of results for comparison and comments on global best solution.