Power Flow Analysis of Addis-Djibouti Railway Power Supply System Using ETAP

The electric railway system represents one of the largest sources of unbalances in the three phase power system. As the traction load of electrified railway belongs to high- power nonlinear single-phase load, it will bring power quality problems such as harmonics and three-phase unbalance to the power system after being connected to the power grid. Therefore, it is necessary to evaluate the impact of the electrified railway operation under different conditions on the power quality of the system substation. In this paper a detail study of power flow analysis and an overview of the power quality for Addis-Djibouti railway line by taking Adegala and Hurso 230kV traction substation as case study is presented. The power flow analysis is done for determining the operation of existing system and also in planning the future expansion of the power system. A case study of modeling and simulation of the actual Adegala and Hurso 230kV traction substation were implemented with the Electrical transient analyzed programme (ETAP) software. Harmonic voltage and current calculations were made to determine whether the injected harmonic currents from the train loads caused unacceptable overvoltage at the point of common coupling (PCC). The simulation results showed that the total harmonic distortion (THD) of voltage is the highest at the point of the traction substation where the traction load is connected. The above mentioned harmonics in the THD are higher than the limits specified by IEEE standards 519-1992.The power flow analysis result shows that the bus voltages outside their specified limits of 95%-105%.Analysis for pre and post contingency event was carried out and the result shows that the system does not have enough redundancy to withstand any fault line voltage.