Research on the sheath grounding current in High-speed railway feeder cable

With the rapid development of High-speed railway and Electric power system in China, Electrification railway special 27.5 kV feeder cable has been widely used in the domestic High-speed railway. When AC current flows through the conductor in cable, the shielding layer will generate a corresponding induced electromotive force of which the magnitude is mainly proportional to length of the cable and value of the current in the conductor. When value of induced electromotive force on the sheath is too large, it may cause the grounding fault of the cable and endanger the safety of the people and the equipment, so the grounding of cable sheath is necessary. Excessive grounding current on metal sheath of single-core high-voltage cable will bring massive additional loss to the cable, which reduces the cable´s current carrying capacity and safe operation lifetime. In this paper, the simulation software PSCAD/EMTDC is used to build the model of the High-speed Railway All-parallel AT Traction Power Supply System, build the model of cable sheath single-grounded way, cable sheath midpoint-grounded way and cable sheath cross connection grounding way. Using PSCAD/EMTDC simulation software to measure the grounding current of cable sheath under different length of cable, graph of grounding current in cable sheath is obtained. This paper use the cable sheath grounding current and graphical analysis the sheath grounding current variation trends. Reveal the variation of grounding current with cable length.