Reliability Assessment and Enhancement of Distribution System (Case Study: Adama Mobile Substation Feeder M-1)

Abstract

The study evaluates the current state of the distribution system, identifies its vulnerabilities, and proposes improvement strategies. It starts with a thorough reliability assessment using historical data from 2013 to 2015 E.C., load profiles, and system performance metrics. The assessment reveals that feeder M-1 experiences an average of 220 interruptions per customer per year, with an average duration of 306.12 hours per customer per year. These figures are substantially higher than the Ethiopian Electric Agency (EEA) standards, which set the SAIFI (System Average Interruption Frequency Index) at 20 interruptions per customer per year and the SAIDI (System Average Interruption Duration Index) at around 25 hours per customer per year. Key indicators such as outage frequency, duration, and customer impact are analyzed to evaluate the system's current reliability. Upon identifying critical areas of concern, the study proposes targeted enhancements, focusing primarily on the integration of advanced technologies. These include the strategic deployment of automatic outdoor reclosers, sectionalizers, and the integration of tie-switches into the system. These technologies aim to optimize fault isolation, facilitate rapid system reconfiguration, and improve overall resilience. The case study involves simulations using Electrical Transient Analysis Program (ETAP 19.0.1) software and real-world data analysis to demonstrate that the system's reliability can be significantly improved with economically and technically justified solutions. Four different mitigation cases are evaluated to improve system reliability. The case with the lowest SAIDI, SAIFI, and Expected Energy Not Supplied (EENS) at a reasonable cost is selected. The results show that the reliability of Adama city's feeder M-1 has improved by 74.09% for SAIFI, 74.13% for SAIDI, and 74.16% for EENS compared to the existing system under the simulated best option. The economic feasibility analysis indicates that the selected solution results in annual cost savings of 4,658,760.04 ETB from the unsold energy of feeder M-1, with a payback period of 0.77 years for the investment. Additionally, the societal satisfaction derived from these improvements is considered an invaluable benefit.