Impact of High-Voltage Primary Supply Lines in the 2 $\times$ 25 kV–50 Hz Railway System on the Equivalent Impedance at Pantograph Terminals

The High Speed/High Capacity railway lines use the 2 × 25 kV-50 Hz power system. It is supplied at high voltage by dedicated primary lines that can be placed in close proximity to the railway line. In railway traction systems, locomotive power electronic converters and auxiliary systems are important harmonic sources. Resonance phenomena can cause harmonics amplification, with consequent problems as voltages distortion and electromagnetic interference with track circuits and communication lines. Electromagnetic conducted emissions in railway traction systems are strongly related to the equivalent impedance at the pantograph terminals. This paper presents detailed models of the railway system, also including the primary line, with the aim to evaluate the impact of the primary line on the equivalent impedance seen by the rolling stock, with particular regards to its resonance frequencies.