Fault Analysis of AC Traction Power Supply System using Autotransformer with Variable Tap Changer

초록

AC traction power supply system in Korea consists of receiving unit, main transformer, catenary, and autotransformer. The catenary is connected to trolley wire including messenger wire, feeder line, and rail including FPW (fault protection wire) and earth wire. Autotransformer is equipped every about 10km in catenary and reduces voltage drop and electromagnetic interference. However, the voltage supplied in train and the voltage at the end of feeding section are going down due to increasing electric load and reduced headway in feeding system. This paper presents the method to enhance the voltage supplied in train. Traction power consumed in train is supplied between trolley wire and feeder line. To increase this voltage, the usefulness of new autotransformer which has variable tap is considered. The increasing of autotransformer turn ratio between trolley wire and rail results in enhancement of collecting voltage of train. To examine the effect of proposed method, the simulation using PSCAD/EMTDC is performed. Through simulation, the voltage enhancement of about 7% in train is obtained. In addition, the fault analysis between trolley wire and rail is also performed to verify stability of traction power supply system according to variation of autotransformer turn ratio.