The increase in disturbances at frequencies higher than 10 kHz in Medium Voltage (MV) grids has led to new needs related to the characterization of Instrument Transformers (ITs) involved in the monitoring of these disturbances. In this context, this paper presents a novel generation and measurement setup for the characterization of MV Voltage Transformers (VTs) up to 150 kHz. The proposed approach is based on the generation of test signals composed of a tone at MV and power frequency and one at reduced amplitude and higher frequency. By implementing a suitable compensation technique, the traceability of the two tones is ensured before their combination.

A measurement system is proposed for characterizing wideband current transformers (CTs) using a precision power analyzer as a sampling current ratio bridge. This approach simplifies the setup significantly with respect to conventional, primary measurement systems, with only a limited reduction in measurement uncertainty. Initial characterisation of the measurement system shows that it is able to achieve uncertainties of less than 50 ppm and 30 μrad for CT ratio error and phase, displacement, respectively over the frequency range from 50 Hz to 5 kHz, provided a calibrated wideband reference CT is available with suitably low uncertainties. This makes the system ideal for use by NMIs and in industrial applications that do not need the ultimate accuracies achieved by primary CT calibration setups.

High-Frequency Distortion (HFD) in both Low Voltage (LV) and Medium Voltage (MV) grids is gaining growing interest from the scientific and technical community due to its increasing occurrence and the issues they can cause. Furthermore, the phenomenon of HFD is expected to rise as it primarily stems from newly installed devices essential for achieving decentralized generation from renewable sources. To monitor HFD in MV grids, the use of Instrument Transformers (ITs) is essential to scale down voltages and currents to levels compatible with the input stages of Power Quality (PQ) instruments. In this respect, the recently released edition 2 of the IEC 61869–1 standard extends the IT accuracy class concept up to 500 kHz. However, within the IEC 61869 standard family, guidelines for testing ITs only exist at power frequency, lacking information on the procedure and setup for assessing the frequency behaviour of ITs. This paper proposes a flexible architecture for generating realistic currents with superimposed HFD. It involves the use of two current sources, one devoted to the generation of a fundamental tone at rated amplitude (theoretically up thousands of ampere) and frequency (DC or AC 50/60 Hz) and one for the superimposition of tones at reduced amplitude and frequencies in the HFD range. Through preliminary tests, the applicability of this proposed architecture has been experimentally validated and it is presented in this paper.

The increasing integration of renewable resources in the energy mix of countries leads to a certain degradation of the quality of electricity due to the use of electronic power converters. The latter, composed of switching components, can introduce high frequency harmonics up to 150 kHz into the network. However, the international standards and state-of-art literature of instruments transformers (ITs) do not adequately cover or even address methods, techniques, parameters, and metrological requirements to be followed during power quality (PQ) measurements in case of frequencies greater than tens of kilohertz. In this framework, this paper proposes a new method and a measurement setup, performed with economical instrumentation, for characterizing two medium voltage (MV) low-power voltage transformers (LPVTs) in the extended frequency range 9 – 150 kHz. In detail, this work applies the “sinc-approach” which is a new characterization procedure, previously designed by the authors, that has several advantages enumerated later. After the description of the scenario behind this work, the measurement setup, tests, and results are described in depth in order to propose a preliminary simple and low-cost harmonic characterization procedure of LPVTs in the frequency range from 9 kHz to 150 kHz.

With the widespread diffusion of power converters able to be directly connected to Medium Voltage (MV) grids, there is the need to measure high frequency distortion, that is from 9 kHz up to 150 kHz. Inductive Voltage Transformers (VTs) are still the most installed voltage transducers in the power systems, but the knowledge of their behaviour in this frequency range is still an open issue. The aim of this paper is to analyse the behaviour of inductive VTs from 9 kHz up to 150 kHz. A commercial VT has been tested and the results show that the nonlinearity of the iron core can influence the behaviour of inductive VTs at least up to 150 kHz.

Instrument transformers (ITs) play a crucial role as interface elements in power systems, enabling the acquisition of electrical quantities necessary for assessing system health.
Consequently, they have been a focal point in research, with numerous studies aiming to enhance their performance in field applications. One critical issue affecting the accuracy of ITs is the differentiation between type and routine tests, which
underscores the need for individual or group error compensation. This study investigates the limitations of group error compensation techniques for ITs, providing experimental evidence to demonstrate their potential drawbacks. Specifically, low-power current transformers, such as Rogowski coils, were evaluated to examine variability among individual devices. The
study tested three series of six devices from three manufacturers under varying temperature conditions. The findings reveal
significant variability among the tested devices, indicating that group error compensation often degrades the accuracy of ITs.
These results highlight the importance of considering individual error characteristics to ensure optimal performance in practical
applications.