Power distribution network reliability remains a critical operational bottleneck in developing sub-Saharan electrical grids, where frequent unprogrammed interruptions severely degrade industrial and domestic productivity. This study presents a rigorous empirical reliability evaluation of a 132/33/11 kV urban distribution architecture (Owerri Network Grid) utilizing a three-year operational fault dataset. Standard quantitative reliability indices, including Failure Rate (λ), Mean Time between Failures (MTBF), and Availability (A), were modeled using stochastic formulations. A probabilistic framework relying on the Poisson distribution was developed to model monthly fault frequency distributions, which were validated using Chi-Square ( ) goodness-of-fit testing. The empirical data revealed severe performance degradation over the timeline with total annual faults escalated by 52.75 %, driving the cumulative network failure rate from 0.4632 faults/hr to 0.7075 faults/hr. Concurrently, the system's operational MTBF decayed by 34.52 %, dropping from 2.1589 hours to 1.4135 hours. Statistical modeling demonstrates that the system's probability of continuous power delivery drops to a mere 10.54 % within a standard 10-hour operating window. A 24-hour projection of the stochastic model reveals a near-zero probability (0.5%) of uninterrupted operation, confirming that continuous daily power delivery is practically unattainable under the current network architecture. Chi-Square hypothesis testing confirmed that fault distributions adhered firmly to stochastic Poisson processes during stable operational windows but experienced deviations driven by intense seasonal environmental stresses and compounding infrastructural degradation. The findings emphasize that the network operates far below international reliability benchmarks, highlighting an urgent need for automated fault isolation, network topology optimization, and targeted asset renewal.
Idiode et al. (Thu,) studied this question.