Browsing by Author "Eleni Sisay"

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    Study on Improvement of the Existing Power Reliability of Addis Ababa Light Railway Transit
    (Addis Ababa University, 2023-08) Eleni Sisay; Getachew Biru (PhD)
    The DC Railway Traction Power Supply System is a widely used technology around the world, particularly in urban and inter-urban regions. The system operates on standard DC traction voltages of 750 V, 1500 V, and 3000 V, which require less electrical clearance than the AC Railway Traction Power Supply System catenary. However, power interruptions can have a significant impact on the system. In the case of AALRT, frequent power interruptions led to thousands of passengers being evacuated from subway cars and stranded at stations. This tesis analyses the reliability of the Addis Ababa Light Rail Transit (AALRT) Traction Power Supply System (TPSS) using interruption data collected from AALRT, Ethiopian Electric Power (EEP), and Ethiopian Electric Utility (EEU). The data includes the number of customers interrupted, number of trips cancelled due to power interruption, daily number of customers served, daily customer interruption duration, number of times the power interruption occurred, number of passenger flow in both lines, and number of passengers interrupted. The causes of power interruption from EEP and EEU sides and duration of power interruption from incoming line 132/15kV are also included. Then, reliability indices are calculated and analysis results indicate that the highest mean time between failures (MTBF) was 2688.98 hours on the East-West (EW) line in 2019 G.C. and 4705 hours on the North-South (NS) line in 2020 G.C from the collected data. The highest duration of power interruption recorded was 804.47 hours on NS in 2019 G.C, and the highest frequency of power interruption recorded was 154 interruption/year on NS in 2020 G.C. In this thesis, two power reliability improvement technologies, substation reconfiguration and distributed generation, were analysed. The thesis was modelled in Matlab Simulink and the results were compared and best reliability mitigation techniques were identified. Substation reconfiguration by using redundant line has been found the best alternative for improving the power reliability for AALRT. As per the model developed, system average interruption frequency index and system average interruption duration index of 10.0490 interruptions/year and 24.0280 hr/customer/year, respectively have been achieved. This method is optimal in terms its applicability and cost.