RAM analysis for decision-making in electrical equipment of the Penipe medium voltage subtransmission feeder

Abstract

Introduction: the reliability of electricity supply depends largely on the behavior of non-repairable equipment installed in distribution networks, whose failure condition requires direct replacement. At Empresa Eléctrica Rio, the lack of a systematic quantitative analysis of this equipment limited maintenance planning to a mostly reactive approach. Objective: this study aimed to apply reliability engineering methodologies to non-repairable equipment on the medium-voltage feeder in the Penipe sector, to estimate indicators that support maintenance planning and asset management. Methodology: the research followed a mixed, descriptive, and applied approach, based on a database of more than 2500 failure events recorded between November 2023 and October 2025. Times to failure were fitted using a two-parameter Weibull distribution, and repair times using a Lognormal distribution, to calculate reliability, maintainability, failure rate, and availability. Results: the results show a shape parameter of β = 1.3, indicating a gradual wear-out process rather than random failures. The average MTTF was 562 h, with monthly dispersion below 4%, and the average MTTR was 13.9 h, resulting in an average intrinsic availability of 98%. The availability projection as a function of operating time confirmed this value, stabilizing above 95% after 300 hours. Conclusions: it is concluded that the analyzed feeder shows an identifiable wear-out behavior and high operational availability, sustained mainly by short repair times rather than the absence of failures. The study contributes a replicable procedure for quantitatively characterizing non-repairable equipment using existing administrative records, without the need for additional instrumentation, and establishes a methodological baseline applicable to other feeders in the network. General field of study: Maintenance. Specific field of study: Reliability Engineering. Type of study: Original article.