Recommendations for the calculation of the total disturbing return current from electric traction vehicles

The superposition of the conducted interference produced by multiple electric traction vehicles into a track section is considered in the frequency range up to 20 kHz. The subject is important not only for estimation of the disturbance produced by new rolling stock in plausible traffic conditions, but also for each railway operator to fix adequate limits for the return current of each unit. The analysis is performed on a reference ac single track line of overall 50-km length. First, the sources of interference are classified, with particular attention to the synchronization issue and phase displacement. Then, the railway line properties as the mean of conductive coupling are identified (attenuation and phase rotation versus frequency and length). Last, a preliminary attempt is made to derive summation rules for disturbance from different vehicles