Fast Voltage Stability Indices Model for Voltage Collapse Prediction in Distribution Networks: A Nigerian 33/11 kV Feeder Study
Keywords:
Fast voltage stability index, Improved power quality, Line voltage stability factor, Line voltage stability index, Power network assessment (Borokiri), Voltage collapseAbstract
Voltage instability is a primary driver of blackouts in the Nigerian grid, characterised by persistent abnormal voltage levels. This study identifies a bus nearing collapse defined by IEEE as the inability to maintain stability following a disturbance and evaluates three stability indices: the Fast Voltage Stability Index (FVSI), Line Voltage Stability Index (LVSI), and Line Voltage Stability Factor (LVSF). Using a two-bus network quadratic model, the south feeder of Borikiri Town was simulated in ETAP 19.0.1. Initial results showed violations exceeding the IEEE ±10% threshold, with receiving-end voltages dropping to 8.4 kV (on a 33/11 kV system). To remediate the system, an 18 kVAr capacitor bank was introduced. Post-compensation, the receiving-end voltage improved to 10.85 kV, reflecting a 2.45 kV net improvement and a minimal 1.36% voltage drop, successfully bringing the system within IEEE limits. The analysis pinpointed buses 2–3, 5–6, 6–7, and 8–9 as being at high risk of collapse. A comparative evaluation revealed that LVSF provides faster and more accurate predictions than LVSI and FVSI. This superior accuracy is confirmed by Mean Absolute Percentage Error (MAPE) values: LVSF: −3.38, LVSI: −85.655, and FVSI: −99.875. The novelty of this work lies in combining fast voltage stability indices with practical compensation strategies on a real distribution network, thereby offering a computationally efficient and utility-ready tool for early prediction of voltage collapse and improved distribution system planning.
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