Study of Distributed Generation in Improving Power System Reliability (Case study: Addis Center Substation)

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Addis Ababa University


Reliability analysis is a main aspect for power system planning, design and operation. In a country like Ethiopia, which is growing fast, ensuring power system reliability should be given better attention since energy is the main engine for any form of development. The present Addis Center Substation (ADC) has encountered frequent power interruptions and power quality problems. The interruptions are caused mainly by short circuit (SC) and earth fault (EF). There are also planned outages for operation and maintenance purpose. The substation’s System Average Interruption Frequency Index (SAIFI) and System Average Interruption Duration Index (SAIDI) are 152.16 and 144.502, respectively. The substation is not reliable by the standard of Ethiopian Electric Agency (EEA) which set (SAIFI =20 and SAIDI= 25). This reliability gap calls for searching of effective methods for improving the reliability of the distribution system. Among different solutions to power system reliability problems, integrating Distributed Generation (DG) to the current network is evaluated in this thesis. Distributed generation is a generation of an electric power close to the load. The resources are mini hydro, photovoltaic Array (PV), fuel cells, wind generators, micro turbines and so on. In this thesis, based on availability of the resource, cost factors, and utilization area, Microturbine/Fuel cell hybrid system of is selected from other distributed generation resources. The size of a single DG is 3.5MW and fed to the grid as backup when there is an interruption. Simulation studies using DigSilent software for reliability analysis is carried out. So, the main focus of this thesis is studying the improvement of power reliability using DG as a backup. Best location of DG, multiple DGs at the same load point and reliability improvement opportunity with DG has been investigated. One of the feeders, (ADC-7) was studied to investigate the effect of distance of DG to reliability. SAIFI and SAIDI of this feeder without of DG were 249.6 and 186.1 respectively. With the DG option at the end of the line, the simulation result shows that the above indices reduced to 20.46, and 15.75 respectively. Key words: Power System Reliability, Distributed Generation, DG technology, PowerFactory.



Power System Reliability, Distributed Generation, DG technology, Power Factory