In the recent years, much more attention is paid to energy and power quality measurement in railway system. In both the case, the voltage and current transducers play a crucial role and their accuracy could determine the performance level of whole measurement system. To obtain reliable results, the accuracy of transducers should be tested with waveforms as close as possible to real working conditions. To assess the metrological characteristic of DC voltage and current transducers under real operating conditions, this paper presents a calibration set up able to generate up to 6 kV for DC voltage and up to 300 A for DC current. The system is able to generate complex and non-stationary test signals which go beyond the standard characterization procedures. Dynamic tests can be derived from real signals obtained from experimental data. For this aim, a specific software tool was developed and here it is presented.