Vulnerability Assessment of Nigerian 48-Bus 330 kV Transmission Network to Cascading Failure Using Eigenvalue-Based Modal Analysis

This study presents a vulnerability assessment of Nigeria’s 48-bus 330?kV transmission network to cascading failures under multiple contingency scenarios using eigenvalue-based modal analysis. A high-fidelity simulation model was developed in NEPLAN, comprising 48 buses, 67 transmission lines, and multiple generating stations. Modal analysis was employed to diagnose voltage instability by evaluating participation factors associated with the system’s lowest-frequency oscillation modes. The results reveal that northeastern buses, including Jalingo (0.2056), Maiduguri (0.1982), Yola (0.1925), Damaturu (0.1548), and Gombe (0.1227), exhibit dominant modal participation, indicating heightened vulnerability to reactive power disturbances. Transmission corridors such as Makurdi–Jos (1.000), Jos–Gombe (0.6875), and Ugwaji–Makurdi (0.3467) demonstrated strong modal sensitivity, suggesting their critical role in fault propagation pathways. Generator participation analysis identified Okpai GS (1.0000) and Shiroro GS (0.4357) as key dynamic influencers, underscoring their strategic importance in system stability. The findings highlight the grid’s susceptibility to cascading failures, particularly in weakly meshed Northeastern regions with limited reactive power support. Modal analysis proves to be an effective diagnostic tool for identifying instability-prone elements and guiding targeted resilience interventions. The study recommends strategic deployment of reactive compensation devices and topology reconfiguration to mitigate instability and cascading failure risks and enhance grid robustness under multi-contingency conditions.