A Method for the Measurement of Digitizers’ Absolute Phase Error

A lot of engineering applications, from telecommunications to power systems, require accurate measurement of phase angles. Some of them, like synchrophasor measurement and calibration of instrument transformers with digital output, in order to reach high phase measurement accuracy, require the knowledge of phase error of digitizers. Therefore, in this paper a method for the measurement of digitizers’ absolute phase errors is proposed. It adopts a sinewave and two square waves, that are the digitizer sample clock and a phase reference signal. Combining the measurements of the relative phase differences between the adopted signals it is possible to accurately evaluate the absolute phase error of a digitize

A Set-up for Static and Dynamic Characterization of Voltage and Current Transducers used in Railway Application

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

Synchronized Measurement System for Railway Application

In the light of the recent European directives that regulate railway networks in EU, in order to implement the monitoring and controlling of the railways power supply network, an accurate and reliable knowledge of the exchanged energy between the train and the railway grid is an essential task. Therefore, a measurement system for railway applications must accurately evaluate energy and power quality. In order to do this, the synchronization to a common time reference of all the measurement devices of the network is mandatory. In this paper, a flexible measurement instrument for analysing different types of signals that could be found in railway systems is presented. The proposed instrument has extreme flexibility about the nature of input signals and it implements a synchronization technique to the absolute time via Global Positioning System (GPS). The implementation of the measurement system, along with evaluation of synchronization accuracy, is discussed

Taratura di trasduttori per cortocircuito mediante digitalizzatori ad elevata precisione

Le prove di cortocircuito sono essenziali per la validazione della sicurezza e dell'affidabilità delle apparecchiature elettriche. Queste attività devono essere eseguite in conformità con le norme di prodotto, che si riferiscono allo standard IEC 62475 [1], relativo alle tecniche di prova ad elevata corrente. Al fine di garantire la tracciabilità del sistema di misurazione dei laboratori di prova, l'INRIM (Istituto Nazionale di Ricerca Metrologica) ha sviluppato negli anni un sistema di riferimento in grado di tarare i dispositivi direttamente in condizioni dinamiche comparabili a quelle presenti durante i test di cortocircuito

Improvement of Agilent 3458A Performances in Wideband Complex Transfer Function Measurement

Digital multimeters (DMMs) Agilent 3458A are valuable devices in accurate characterization of voltage transducers. Five selectable ranges, from 100 mV to 1 kV, high input impedance and accuracy make this device the state of the art. The paper focuses on the correction of the multimeter frequency response when used in Direct Current digitising mode (DCV), to allow post-correction of the errors introduced by the digitizers. To this end, two different approaches for the identification of the multimeter input complex filter function up to about 100 kHz are proposed. They are, respectively, based on the identification of the complex filter transfer function considering the input stage of the DMM as a black box and on the estimation of the parameter of the DMM input stage. The two methods are validated in a test case and equivalence of the results obtained is found. As a further verification, a deep investigation of DCV and direct sampling mode is performed when the zero level trigger mode is set

Improvement of Agilent 3458A performances in wideband complex transfer function measurement

The phase and ratio errors of transducers for distribution electrical grids can be measured, in a wide frequency range, by a synchronized couple of digitizers Agilent 3458A working in DCV mode. The high metrological performances of the digitizers is degraded by the input low pass filter cut-off frequency, which depends on the selected range. This paper proposes a technique to identify and model, for each range, the filter complex function up to several tens of kilohertz. First tests show its potentiality in reducing the errors introduced by the digitizers, when set on different ranges, in frequency calibration of voltage/current transducers

Sensorless Commissioning and Control of High Anisotropy Synchronous Motor Drives

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