This paper presents a detailed model of the AC 2x25 kV High Speed/High Capacity (HS/HC) railway lines in order to dynamically analyze the electric systems. The power quality analysis reported here is important considering that these lines are directly connected to the high voltage (HV) transmission grid and also that the control and auxiliary devices are directly connected to the feeder wire. The accuracy of the results, obtained by carrying out numerous simulations, was confirmed via comparison with dedicated experimental surveys on the lines during their operation