Reliability Analysis of Power Transmission Infrastructure in the North Central Grid Using Failure Mode Models

The reliability of Nigeria's national electricity grid, particularly the transmission infrastructure serving the North Central zone managed by the Transmission Company of Nigeria, is critically compromised by ageing equipment, vandalism, and inadequate maintenance investment. This study applies reliability engineering analysis, including failure mode and effects analysis, Weibull survival modelling of equipment failure time data, and fault tree analysis, to quantify the reliability characteristics of transmission towers, conductors, and substation transformers across the Shiroro-Birnin Gwari and Jebba-Onitsha 330 kV corridors. Failure time data for 840 equipment items over the period 2017 to 2023 are obtained from the TCN asset management database. Weibull parameters are estimated by maximum likelihood separately for each equipment class. System-level reliability metrics including mean time between failures, system availability, and expected number of failures per year are computed from component-level Weibull models using fault tree logic. The critical transmission path reliability is estimated at 87.3 percent annual availability, compared to an international benchmark of 99.5 percent for comparable grid infrastructure. Sensitivity analysis identifies transmission tower corrosion failure as the single most influential component failure mode, contributing 38 percent of total system unavailability. The study recommends a risk-prioritised maintenance programme targeting the 12 highest failure-risk towers on the Shiroro corridor. Keywords: reliability analysis, Weibull model, transmission infrastructure, fault tree analysis, power grid Nigeria.