Experimental and Simulation Analysis of the Nigerian 330 kV Grid with the New Haven–Nkalagu Sub-Transmission Line Integration

Abstract

This study centered on experimental and simulation analysis of the Nigerian 330 kV grid with the integration of the New Haven–Nkalagu 132 kV transmission line, focusing on load flow performance and protection coordination. A load flow analysis was conducted on the network, incorporating the New Haven–Nkalagu 132kV line via a 330/132kV transformer to assess system behavior during faults. PSAT software in MATLAB was used for modeling, analyzing bus, line, and generator data, ensuring accurate voltage and power flow adjustments for system stability. The substations include New Haven 330 kV, New Haven 132 kV, and Nkalagu 132 kV with transmission voltage levels of 328 kV, 131kV, and 128 kV respectively. These buses had fault current levels of 4000 A, 3000 A, and 2500 A respectively as calculated in the analytical sessions. The test carried out using a portion of the experimental data obtained from the National Control Centre Oshogbo showed an average absolute deviation of 0.9838% between the experimental data and the simulation results further validating the accuracy of the simulation model. Relay coordination analysis for varying fault currents indicated that Nkalagu relay acts as the primary protection, with tripping times significantly reduced as fault current increased. The current tap settings (CTS) for both relays also increased with rising fault levels, reaching maximum values of 8.69 A and 13.33 A for Nkalagu and New Haven, respectively. These results underscore the importance of precise relay configurations for optimal protection. Recommendations for further optimization through adaptive techniques were made to enhance grid performance under varying fault conditions. This research offers practical solutions for improved fault management and relay coordination in future grid expansions.