Comprehensive Assessment of Ferroresonance and its Effects in Selected Distribution Substations in Nasarawa State, Nigeria

Abstract

Ferroresonance in distribution networks generates harmful harmonics, excessive heating, and potential transformer failures, yet limited research focuses on its impact in Nigerian low-voltage systems. This study examines ferroresonance susceptibility in low-voltage distribution transformers, with an emphasis on core saturation, harmonic distortion, and grading capacitance effects under varied operational conditions across substations in Lafia, Akwanga, and Keffi. By analyzing transformer responses from 50V to 500V and harmonic profiles in Delta (1.12Ω) and Star-Grounded (1.53Ω) configurations, the research highlights transformer design's critical role in ferroresonance resilience. Findings reveal that increasing grading capacitance from 90 pF to 1550 pF substantially elevated peak voltages from 0.420kV to 2.400kV (Lafia), 2.450kV (Akwanga), and 2.540kV (Keffi), and currents from 28A, 26A and 27A to 103A, 118A, and 130A, respectively. Voltage THD similarly rose from 6.5%, 6.3% and 6.7% to 35.5%, 38.2%, and 36.0%, respective; with current THD climbing from 7.8% 7.5% and 7.9% to 40.2%, 44.1%, and 42.3% respectively, indicating varying ferroresonance susceptibility across the substations. Delta configurations show lower ferroresonance risk compared to Star-Grounded types, underscoring optimal winding configuration and capacitance management as key resilience factors. Recommendations include targeted harmonic filtering and precise capacitance management to stabilize transformer operation. Future research should consider broader transformer model diversity, adaptive control systems, and machine learning techniques for enhanced ferroresonance risk assessments.