A Randomised Field Trial Methodology for Evaluating Power-Distribution System Reliability in Tanzania

{ "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: $h(t|X) = \\frac{\\beta}{\\eta} \\left( \\frac{t}{\\eta} \\right)^{\\beta-1} \\exp(\\theta X)$, 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