A Scenario-Based Reliability and Voltage Stability Assessment for Expansion Planning in the Nigerian Power System

Abstract

Expansion planning in developing power systems is often constrained by limited data, weak network structures, and competing investment priorities, leading to decisions that inadequately address system reliability and voltage performance. This study presents an integrated assessment framework that combines probabilistic reliability evaluation with steady-state voltage stability analysis to support expansion planning under such conditions. A reduced representation of the Nigerian transmission network is developed in MATLAB using MATPOWER. Reliability is quantified through Energy Not Supplied and Loss of Load Probability derived from Monte Carlo simulation of generator outages, while voltage stability is assessed using the L-index. Three planning scenarios are examined, comprising a base case, shunt reactive compensation, and generation capacity addition. The results indicate that the system maintains acceptable voltage stability margins across all scenarios, whereas reliability performance is significantly constrained by generation inadequacy. Reactive compensation yields negligible impact on both reliability and voltage stability, while generation expansion produces substantial reductions in Energy Not Supplied and Loss of Load Probability. The findings demonstrate that effective expansion planning in developing grids requires explicit identification of dominant system constraints and prioritization of interventions that directly enhance reliability.