Metrological Characterization of a Signal Generator for the Testing of Medium-Voltage Measurement Transducers

Nowadays, voltage transducers in medium-voltage (MV) distribution networks operate in nonsinusoidal conditions while their calibration is still based on simple sine-wave tests. A more significant characterization could be achieved using complex multitone signals. However, this requires an MV generator able to apply arbitrary voltage waveforms to the transducer under test. The authors have recently proposed a simple MV signal generator that can be effectively employed for this purpose. In this paper, the performance of this MV generator has been carefully analyzed. A characterization procedure based on multisine excitation has been proposed and tested. In particular, the main causes of uncertainty have been identified and their impact on the accuracy of the generated voltage evaluated. The analysis considers both linear and nonlinear effects, such as harmonic distortion and hysteresis

EVALUATION OF THE DYNAMIC BEHAVIOUR OF HEAVY CURRENT SHUNTS

A method for the assessment of the dynamic behaviour of heavy current shunts is described, which is based on the evaluation of the shunt frequency response through spectral analysis of input and output measured signals. The method has been tested by applying it to simulated current impulses and experimented in the case of a pulse current, generated by the discharge of a cable capacitance, measured by a thin walled coaxial-tube shunt

Calibration of non-conventional instrument transformers

The paper focuses on the calibration techniques of non-conventional voltage and current measurement transformers. Calibration circuits set up at INRIM are described, which makes use of digital acquisition and numerical analysis of the transducer output. Examples of calibration of non-conventional instruments to be used as on-site references are discussed, which include a system based on Rogowski coil for live-on-site check of measuring current transformers with rated voltages up to 380 kV

A measurement system for the calibration of MV instrument transformers under non sinusoidal conditions

The metrological characterization of instrument transformers is a well-known process when it is carried out under sinusoidal conditions. On the other hand, because of the increasing presence of distorting loads such as power electronics converters, often the voltage and current waveforms cannot be considered sinusoidal. In this scenario, the accurate measurement of harmonic components becomes very important both for billing as well as for power quality monitoring. Therefore, the whole process of instrument transformer calibration should be reconsidered in order to take into account their actual behavior also under these operating conditions. In this paper a new setup for the calibration of MV voltage instrument transformers is presented. It is based on two parts: a voltage generator able to supply the transformer under test with an arbitrary voltage signal and a digital signal processing procedure allowing to evaluate the ratio and phase errors of the transformer with a high accuracy, over an extended frequency range