COMPUTER ANALYSIS OF INTERACTION BETWEEN AC AND DC ELECTRIC TRACTION LINES IN ITALY

When alternating current (AC) and direct current (DC) electric traction lines are located in proximity, attention should be given to the compatibility problems among the systems. The mutual interaction between the two power supply systems caused by the imbalances produced by the single-phase loads in the main supply system of the AC electric installation can cause the AC/DC converters to generate noncharacteristic harmonics. A significant problem is the one related to the possibility that in case of parallel 25 kV - 50 Hz and 3 kV DC lines, electromagnetic files are induced in the track circuits of such an amplitude as to disturb the operation of the signaling system. This paper presents preliminary evaluations on the effects of the imbalances produced by the single phase traction loads, as obtained by simulation programs and compared with the measurements in the test site of Castiglion del Lago, set up by Italian Railways; and the voltages induced in the track circuits in normal operation and during transients calculated by multiconductor models.