Empirical Analysis of Voltage Stability Margins in the Nigerian 330kV Transmission Network Under Increasing Renewable Energy Penetration

This study empirically analyses voltage stability margins in the Nigerian 330kV transmission network under scenarios of increasing renewable energy penetration, filling a critical research gap given the significant solar and wind capacity additions planned under Nigeria's Energy Transition Plan. Traditional Nigerian grid generation mix relies on synchronous hydroelectric and gas turbine machines that provide inherent voltage support through reactive power capability, but their progressive displacement by inverter-based renewables alters the network's voltage stability characteristics in ways that require systematic quantification. A detailed power flow model of the Nigerian interconnected transmission system was constructed in PSSE using published TCN network data, incorporating actual generator dispatch patterns from IBEDC and TCN operational records for 2022 and 2023. Renewable energy scenarios representing 10, 20, 30, and 40 percent of total generation capacity were modelled by progressively substituting thermal generation at identified solar and wind sites. Voltage stability analysis was performed using P-V curve continuation power flow and Q-V sensitivity methods at critical buses across all renewable penetration scenarios. Results show that voltage stability margins at the Abuja, Kainji, and Birnin Kebbi 330kV buses deteriorate progressively with increasing renewable penetration, with the 40 percent scenario reducing the margin at Birnin Kebbi bus to within 8 percent of the voltage collapse point under peak demand conditions. Synchronous condenser installation at two identified locations restores acceptable margins across all scenarios. Keywords: voltage stability, transmission network, renewable energy penetration, Nigeria, power systems.