Harmonic amplitude and harmonic phase angles monitored in an electrified subway system during rush-hours traffic

The paper reports some results of a monitoring activity conducted on the subway system of Rome. Both harmonic amplitudes and phase angles have been monitored at one of the five service entrances during the rush-hours traffic. The subway system provides two railway lines supplied at 1.5 kV DC through several AC/DC converter substations. The power supply of the system is provided at medium voltage level (20 kV) from five different connections to the public grid. Fourteen electrical conversion substations provide the total demand of about 20 MW of the system. The obtained results show that the analysis of harmonic amplitude and in particular harmonic phase angles versus time and scatter plots are useful to better characterize this system and to understand the behaviour of such large non linear loads.