Methodology for the Accurate Measurement of the Power Dissipated by Braking Rheostats

Abstract

The energy efficiency of transportation is a crucial point for the rail and metro system today. The optimized recovery of the energy provided by the electrical braking can lead to savings of about 10% to 30%. Such figures can be reached by infrastructure measures which allow the recovery of the breaking energy that is not directly consumed by the rail system and dissipated in rheostat resistors. A methodology for the accurate estimate of such energy is valuable for a reliable evaluation of the cost–benefit ratio associated with the infrastructural investment. The energy can be estimated by measuring a braking current flowing in the rheostats. The varying duty-cycle associated with the high dynamic variation, from zero to thousands of amperes, makes the current measurement very challenging. Moreover, the digitization of such waveforms introduces systematic errors that affect the energy estimation. To overcome these issues, this paper proposes a technique to measure the power and energy dissipated by the rheostat of a DC operated train with high accuracy. By means of an accurate model of the electrical braking circuit (chopper and rheostat) and the frequency characterization of the current transducer, a correction coefficient as a function of the duty-cycle is estimated. The method is then applied to data recorded during a measurement campaign performed on-board a 1.5 kV train of Metro de Madrid during normal operation. Using the proposed technique, the estimation of the dissipated braking energy is improved by 20%.

Influence of Infrastructure and Operating Conditions on Energy Performance of DC Transit Systems

“…Otherwise, energy may be fed back to reversible TPSs (feeding back the AC utility) and storage systems [19][20][21][22] (particularly useful if the country's local regulations allow energy discounting [23]). As a last option, energy may be dissipated on large onboard resistors [24] to safely limit the pantograph voltage excursion (line voltage limits for European systems appear, e.g., in the EN 50163 [25]).…”

Application of Identification Reference Nets for the Preliminary Modeling on the Example of Electrical Machines

“…The equations defining the EMs are usually presented in a rectangular coordinate system, making it possible to determine the relationships between the relevant component of the space vectors of current or voltage and flux [15]. Hence, the modeling methods for the EMs are based on the measurement of peak-to-peak current with the pulsed voltage supply [16,17], measurement of steady-state characteristics [18,19], measurement of currents and voltages at constant velocity or determination of relevant time characteristics [20,21]. The EMs are most often used in the conditions of constantly changing parameters of the supply voltage (e.g., amplitude and frequency) and load torque [14].…”