Harmonics and PQ events monitoring in an electrified metro-transit system

The paper illustrates some results of a wide power quality (PQ) survey performed on the power supply installations of the metro-transit system serving the city of Rome, in Italy. The system currently includes two railway lines supplied at 1,500 V DC through several AC/DC 3.7 MW rated converters. The power supply of the system is provided at medium voltage (20 kV) from five different connections to the public grid. Fourteen electrical substations provide the total demand of about 20 MW of the system. The survey, currently still in progress, involves monitoring activities aimed at identifying possible PQ problems of various nature. Identification of typical daily patterns of harmonics distortion due to the system is even a task of the current survey.