System impacts evaluation of Tehran-Karaj electrical railway on power transmission system

Connecting the feeder network of electric trains to the supply grids causes the voltage unbalance and harmonic distortion. In this paper, the harmonic impact and unbalance of electric railway load in Tehran-Karaj line on utility grid and generator units of Montazerghaem power plant has been studied by measuring and simulating studies by means of DIgSILENT software. The measurements indicate the severe changes of consumed power in feeder substation of this line´s trains and represent the significant levels of third harmonic in this substation current. According to the development approach of this line and headway decrease and load increase in the future, network condition in two present cases and next development have been separately studied and the results have been evaluated and compared to existing standards.