Integration effect of the electric power supply in the metropolitan urban railway: Focused on the direct operation lines

Seoul subway lines 1 and 4 are directly operated with Gyeongbu/Gyeongwon line and Gwacheon/Ansan line of Korail respectively. As the AC and DC neutral sections are established in directly operated connecting-point due to the electric power supply that makes use of AC power in Gyeongbu/Gyeongwon line and Gwacheon/Ansan line and DC power in line 1 and 4, this section is not only vulnerable in terms of operation stability but also increases the cost of electric power and maintenance cost at those subway sections using DC power. Research for their improvement plans and analysis of its effect revealed that the change of the electric power supply sections from DC to AC can enhance the operation stability, reduce the operation cost, shorten the running time and improve the benefit such as improved service.