Evaluation of energy saving effect of traction power supply voltage in urban electric railway system

The influence of the change of traction power supply voltage in DC electric railway in urban area is evaluated based on the operational data around Tokyo area in East Japan Railway Company. Generally speaking, the relation between traction power supply voltage and efficiency in railway power supply system is contradictive. Higher voltage has advantage in small resistive loss while lower voltage has advantage in wide usage of regenerative power. There is no common knowledge which advantage is superior in DC railway power supply system. In this paper, two examples are analyzed in detail. As a results, higher power supply voltage is appropriate at a substation with high operation density while lower supply voltage is better in a middle operation density substation.