Reliability Assessment of Medium Voltage Underground Cable Network—Saudi Arabia Jeddah Case Study

The reliability of medium voltage (MV) underground cable networks is critical for uninterrupted electricity supply in urban environments, particularly in regions with harsh climatic conditions. This study presents a comprehensive reliability assessment of the MV underground cable network in Jeddah, Saudi Arabia, operated by the Saudi Electricity Company (SEC). A six-year dataset (2019-2024) comprising 435 validated fault records, cable infrastructure data, environmental parameters, and restoration times was analyzed using statistical modeling techniques. The methodology integrates descriptive statistics, Pearson correlation analysis, and probabilistic distribution modeling, including Gamma, Weibull, and Log-Logistic distributions. Goodness-of-fit was evaluated using the Kolmogorov-Smirnov test. Reliability indices (SAIFI, SAIDI, CAIDI) were calculated according to IEEE Std 1366-2012 and benchmarked against NRS 047-1 standards. The results reveal that equipment failures account for 60% of all incidents, with insulation failure (51%), cable joint faults (20%), and termination faults (17%) being the predominant mechanisms. Joint and termination defects collectively constitute 37% of equipment failures. The mean restoration time was 5.56 hours, approximately 79% higher than the SEC national average of 3.1 hours, and failed to meet NRS 047-1 targets for 30%, 60%, and 90% restoration milestones. Temperature exhibited a strong positive correlation with failures (r = 0.954), while load demand also showed strong correlation (r = 0.942). The worst-performing feeder (Hera-Feeder-01) recorded 5 failures in 2023 with a mean restoration time of 17.17 hours. The failure rate increased by 25% from 2019 to 2024, indicating progressive infrastructure deterioration. This study provides actionable recommendations for predictive maintenance, climate-adaptive strategies, and database integration to enhance network reliability. The findings offer practical guidance for utilities operating in environmentally demanding regions.