Distinguishing short circuit and normal operation currents in DC urban light railway systems

DC urban light railway systems are used as public transportation systems in many towns worldwide. In these systems, short circuit currents are often similar, both in steady state magnitude and in rate-of-rise, to normal operation currents. In order to properly set the protection relays, to obtain short circuit discrimination and to avoid nuisance trippings, it is important to analyse short circuit and normal operation current patterns. This paper presents the results of measurement campaigns performed for this purpose on the tram network of Turin, in Northern Italy.