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Active Power Flow Control in Ethiopian High Voltage Transmission Networks Using Phase Shifting Transformer to Enhance Utilization of Transmission Lines

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dc.contributor.advisor Fekadu, Shewarega (PhD)
dc.contributor.author Yemane, Esayas
dc.date.accessioned 2020-12-31T05:50:25Z
dc.date.available 2020-12-31T05:50:25Z
dc.date.issued 2018-06
dc.identifier.uri http://etd.aau.edu.et/handle/123456789/24408
dc.description.abstract The electricity supply industry of Ethiopia is undergoing a major transformation that requires a redefined approach to increase the utilization of existing transmission line assets. Overloading of transmission lines in a power system sometimes result stability issues, which may lead to unwanted tripping or failure of equipments. The cause could be uneven loading of interconnectors or parallel transmission lines in meshed networks due to different impedances caused by the tower geometry, conductor sizing, number of sub-conductors and line length. Under these conditions, to ensure economical and reliable operation of the grid, active power flow through the lines should be controlled within their capability limits. In view of above, the power flow needs to be controlled in order to enhance utilization of high voltage transmission lines and secure the power system. Thus Control of power in AC network requires special technology to be implemented on case to case basis. Operating efficiency of electric transmission system can be improved by using appropriate Flexible Alternating Current Transmission System (FACTS) devices. Phase shifting transformer is one of the FACTS families, which can be used for power control in ac network. This thesis presents a study on active power flow control within Ethiopian network for optimum utilization of transmission lines using phase shifting transformer (PST). The study is performed first by reviewing literatures on the use of phase shifting transformers how to redirect active power flow in transmission networks throughout the world. To demonstrate the active power flow control in the network, a 400/400 kV phase shifting transformer having a size of 685 MVA with a phase shifting angle range of -200 to+200 and the high voltage transmission networks was modeled using PSSE software(Power System Simulation for Engineers) for the peak load of 2040 MW in the year 2017. From the power flow studies/solution, various overloaded and under loaded transmission lines are identified. By varying the phase angle of the phase shifting transformer, several simulations are conducted to investigate the impact of PST on the active power flow distribution. In this study, it has been demonstrated that the active power flow patterns which originally flow via the low impedance and lower voltage system is fully controlled and restructured using phase shifting transformer. By varying the phase shifting transformer angle, the active power flow in the transmission lines can be redirected towards the alternate high voltage path. As the Phase shifting transformer angle increased from -20° to +20°, the loading of Wolayta - Gibe II and Sebeta IIGibe II 400kV transmission lines vary from 4% to 35% and 11% to 42% respectively. Similarly, Gelan - Wolayta400kV transmission line load increases from 15% to 43% as the Phase shifting transformer angle decreases from +20° to -20° Conventional ways of solving the network bottlenecks based on reinforcement and building new transmission lines cannot be taken as sufficient and fast due to the problems of acquiring new corridors and environmental limitations. Installation of Phase Shifting Transformer in the transmission network is a better solution for controlling the active power flow and effective utilization of existing high voltage transmission network assets. en_US
dc.language.iso en_US en_US
dc.publisher Addis Ababa University en_US
dc.subject PSSE en_US
dc.subject phase shifting transformer (PST) en_US
dc.subject power flow control en_US
dc.subject FACTS devices en_US
dc.subject phase shifting angle en_US
dc.title Active Power Flow Control in Ethiopian High Voltage Transmission Networks Using Phase Shifting Transformer to Enhance Utilization of Transmission Lines en_US
dc.type Thesis en_US


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