Today's technology and trend for clean energy, made electrified traction systems more and more popular around the world. As number and capacities of those systems increase, electrical modeling of those systems became a must for power quality studies and dynamic distribution system analysis. However, those models have inaccuracies due to electrical parameters and high computational burden. This paper proposes a linearized DC catenary line model for real subway systems, which has a little computational burden. Moreover, the parameter approximations employed by the method provides more accurate results. The proposed method is validated using real measurement data.