"background": "Power-distribution reliability in sub-Saharan Africa is critically understudied, with existing assessments often relying on aggregated utility data or theoretical models that fail to capture localised, real-world performance of equipment under diverse operational conditions. ", "purpose and objectives": "This article presents a novel field-trial methodology designed to empirically evaluate the reliability of medium-voltage distribution equipment, specifically pole-mounted transformers and switchgear, within a national grid. ", "methodology": "We detail a stratified, cluster-randomised field trial design. New equipment units are randomly allocated to distinct geographical clusters within the distribution network. Reliability is measured via time-to-failure analysis, with data collected through automated meter reading and scheduled inspections. The primary analysis employs a Weibull proportional hazards model: h (t|X) = \\{\ \ (\ \) ^\-1 \ (\ X), where X represents covariates including environmental cluster and load type. Inference is based on robust standard errors clustered at the feeder level. ", "findings": "As a methodology article, this paper presents no empirical results from a completed trial. However, the proposed design is validated through a simulation study, which indicates that the methodology can detect a 15 percentage point improvement in survival probability at 36 months with 80% power, given an assumed baseline survival rate of 0. 70. ", "conclusion": "The described randomised field trial framework provides a rigorous, evidence-based approach for quantifying the in-service reliability of power-distribution assets in a real-grid environment. ", "recommendations": "Utilities and researchers should adopt randomised field trials for major equipment rollouts to generate high-fidelity reliability data. Future applications should incorporate longer-term corrosion and mechanical stress monitoring. ", "key words": "distribution reliability, field trial, randomisation, survival analysis, power infrastructure, asset management", "contribution statement": "This work provides the first formalised methodology for implementing randomised controlled trials in
Abasi Mwinyimvua (Tue,) studied this question.