Analysis on Extreme Distance of Power Supply for Urban Rail AC Power Supply System

The power supply distance is an important indicator to measure the power supply capacity of a traction system, and has a practical impact on the stability and economic operation of the system. The urban rail AC power supply system uses the cable structure of the traction network, which has the outstanding characteristics of stable and large-capacity transmission. Therefore, it is of great significance to quantitatively study the power supply distance of the system. In this work, the extreme distance of power supply is analyzed theoretically. According to the circuit topology characteristics of the system, the traction network impedance as well as traction network voltage loss and rail potential are deduced for a single vehicle and multiple vehicles. First, by the natural power comparison between the overhead line and the cable in the traction network, the extreme distance of power supply is calculated in the cases of different cable cross-sectional areas. Secondly, the extreme distance of power supply is analyzed with the constraint of the voltage loss at the peak operating of the system. Finally the rail potential values prescribed in existing electrified railway standards are used as constraints to analyze the maximum short loop length of the system. In simulation, the maximum single-section power supply length of the urban rail AC power supply system can reach 9.31 km. When the main substation is located in the middle of the line, the extreme power-supply distance can reach 84.22 km.