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The European community for over a decade is supporting scientific and technological studies in order to make public transport low environmental impact. The metrological community plays a fundamental role in fostering this improvement. To this purpose, the paper describes the measurement setup and the results of an on-board DC train measurement campaign devoted to the accurate estimate of the energy exchanged between the locomotive and the DC feeder and the electrical energy wasted during the braking stage. These information are fundamental in the accurate determination of the energy saving margin, therefore, in the decision-making related to the infrastructure investment devoted to the energy efficiency improvement such as installation of reversible substation or on-board storage systems. Moreover, the paper provides a scientific contribution in the power quality definition for DC 3 kV railway systems.

DC railways are characterized by particularly intense arcing caused by pantograph detachment, due to the large current intensity and the general implementation of onboard resonant filters, whose transient response is triggered by electric transients including electric arcs. Electric arc depends on the train speed (the relative speed between the sliding contact over the pantograph and the hot spot on the catenary system), the intensity of the collected pantograph current and the line voltage level. Electric arcs are broadband in nature and can trigger the system transient response dominated by the resonant filter, besides interfering with the operation of onboard equipment (such as for energy conversion and metering).