This paper investigates the possibility of using simplified test methods for the characterization of IT frequency response in the supraharmonic range. Unlike the traditional reference methods, the simplified method relies on generating low-voltage and low-current signals, which are easier to implement in testing and manufacturers' laboratories. This method has been developed as a valid and rigorous alternative to the reference method, with results obtained from the laboratories of different National Metrology Institutes (NMIs). An inter-laboratory comparison has been conducted on two commercial current and voltage transformers to evaluate the deviation between results obtained by the reference method and those obtained through the simplified method. The experimental results present remarkable consistency between the two methods, with deviations mostly contained within $\pm0.5$~\% and $\pm1$~crad for ratio and phase errors, respectively.

Within the modernizing energy infrastructure of today, the integration of renewable energy sources and direct current (DC)-powered technologies calls for the re-examination of traditional alternative current (AC) networks. Low-voltage DC (LVDC) grids offer an attractive way forward in reducing conversion losses and simplifying local power management. However, ensuring reliable operation depends on a thorough understanding of DC distortions—phenomena generated by power converters, source instability, and varying loads. Two complementary traceable measurement chains are presented in this article with the purpose of measuring the steady-state DC component and the amplitude and frequency of the distortions around the DC bus with low uncertainties. One chain is optimized for laboratory environments, with high effectiveness in a controlled setup, and the other one is designed as a flexible and easily transportable solution, ensuring efficient and accurate assessments of DC distortions for field applications. In addition to our hardware solutions fully characterized by the uncertainty budget, we present the measurement method used for assessing DC distortions after evaluating the limitations of conventional AC techniques. Both arrangements are set to measure voltages of up to 1000 V, currents of up to 30 A, and frequency components of up to 150–500 kHz, with an uncertainty varying from 0.01% to less than 1%. This level of accuracy in the measurements will allow us to draw reliable conclusions regarding the dynamic behavior of future LVDC grids.

Energy efficiency is an important issue in industry, especially with the ever-increasing consumption of electrical energy. The power quality and the traceability of metering devices are essential when integrating energy metering systems for energy efficiency. This management requires an understanding of electrical current events such as pulse and transient currents. Current transducers are widely used to measure these electrical current events up to a few megahertz. Their use makes it possible to measure not only the main current flowing through the transducer, but also the bypass current that affects electrical equipment. Calibration of these sensors up to a few megahertz then becomes an essential step. Currently, most calibration methods are limited to 100 kHz frequency for a current of 10 A. This paper presents an improvement of a traceable calibration methodology for current transducers up to 10 A and 1 MHz, thus increasing, by 10 times, the current level for such high frequency applications. This calibration methodology is based on a metrological traceability chain (uninterrupted link to the International System of Units) with respect to a calculable current shunt and is currently the only traceable method for calibrating current transducers at 10 A and up to 1 MHz. The uncertainty obtained for the transimpedance ratio is less than 0.2%, which is considerably reduced with respect to the existing capabilities.

This paper describes a new EU-co-funded project on metrology support for enhanced energy efficiency in DC transportation systems (e-TRENY). The project involves 5 national metrology institutes, 3 universities, 1 metro operator, and 1 consulting group. Research focuses on the following topics: i) new calibration facilities for DC transducers (up to 3 kV, 1 kA) under dynamic conditions, ii) accurate on-site losses of the converter group (power transformer - AC/DC bidirectional converter, DC/DC converter) operating in DC substations, iii) energy saving performance of transportation systems with non-conventional DC substations.

Instrument transformers (ITs) play a key role in electrical power systems, facilitating the accurate monitoring and measurement of electrical quantities. They are essential for measurement, protection, and metering in transmission and distribution grids and accurately reducing the grid voltage and current for low-voltage input instrumentation. With the increase in renewable energy sources, electronic converters, and electric vehicles connected to power grids, ITs now face challenging distorted conditions that differ from the nominal ones. The study presented in this paper is a collaborative work between national metrology institutes and universities that analyzes IT performance in measuring distorted voltages and currents in medium-voltage grids under realistic conditions. Both current and voltage measuring transformers are examined, considering influence quantities like the temperature, mechanical vibration, burden, adjacent phases, and proximity effects. The study provides detailed insights into measurement setups and procedures, and it quantifies potential errors arising from IT behavior in measuring distorted signals in the presence of the various considered influence quantities and their combinations. The main findings reveal that the temperature has the most evident impact on the inductive voltage transformer performance, as well as the burden, causing significant changes in ratio error and phase displacement at the lower temperatures. As for low-power ITs, establishing a priori the effects of adjacent phases and proximity on the frequency responses of low-power ITs is a complex matter, because of their different characteristics and construction solutions.

Main text Comparison for ultra-low DC current sources between LNE (France), BFKH (Hungary), NSAI NML (Ireland), IPQ (Portugal), RISE (Sweden), METAS (Switzerland) and TÜBİTAK UME (Turkey). To reach the main text of this paper, click on Final Report . Note that this text is that which appears in Appendix B of the BIPM key comparison database https://www.bipm.org/kcdb/ . The final report has been peer-reviewed and approved for publication by the CCEM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Instrument transformers are largely used to measure voltages and currents in public electricity networks. Their performance is essential for Power Quality measurements. Tests and procedures to estimate the effect of single influence factors are performed according to current standards. However, the instrument transformers are exposed simultaneously to more than one factor. The standardized procedures for their characterization with combined influence factors are under construction in Europe. The work in this paper is focused on the development of a new set-up for the determination of the accuracy and frequency response of medium-voltage transformers within the combined influence factors of temperatures and vibrations. The test set-up includes a platform for the combination of temperature and vibrations, a generating system for harmonics up to 9 kHz superposed with 35 kV, 50 Hz voltage and a reference measuring system. The results of several tests carried out on a 35 kV/100 V/50 Hz voltage transformer in the presence of these influence factors are discussed in this paper. They show that the accuracy and frequency response of the voltage transformers are more influenced by temperature than by vibrations.

The necessity of measuring harmonic emissions between 2 and 150 kHz is outlined by several standard committees and electrical utilities. This paper presents a measurement system and its traceable characterization designed to acquire and analyse voltages up to 230 V and currents up to 100 A with harmonics up to 150 kHz that may occur in smart grids. The uncertainty estimation is carried out and described in detail for both the fundamental and supraharmonics components. From a metrological point of view, ensuring the traceability of current measurements for frequencies higher than 100 kHz and dealing with the complexity of uncertainty determination are bottlenecks related to supraharmonics measurements that this paper proposes an approach to deal with.

Current standard EN 50463-2 indicates the tests and the requirements to be satisfied for an energy measurement system of a traction unit for railway applications. Some of these tests are to be done with several harmonics superposed on the rated voltage, respectively current. However, no calibration systems satisfying the standard requirements were available few years ago. The work performed in the EURAMET project “MyRailS” leads to the development of fictive power sources and reference measurement systems described in this paper. Therefore, it is possible to generate distorted 25 kV-50 Hz voltages with harmonics up to 5 kHz and 90° phase-fired currents up to 500 A with harmonics up to 5 kHz. The generated power is measured by developed traceable reference systems with accuracy better than 0.5%.

The work presented in this paper aims at developing a reference system for laboratory calibration of the Energy Measurement Functions working under AC supply system and actual operating conditions. More precisely, the paper focuses on the design of a fictive power source designed to generate voltage and current waveforms of 15 kV-16.7 Hz and 25 kV-50 Hz, 500 A with harmonics up to 5 kHz.

This paper describes the design of a generic waveform platform for the testing and calibration of power quality analyzers in the frequency range of 2 to 150 kHz. In the electrical grids, the waveform platform can be used to measure the emissions in the frequency range of 2 to 150 kHz. The software architecture of the waveform platform is specified here. In addition, the paper explains the hardware design of the waveform platform. It also includes the applications of the waveform platform. The laboratory setup for the calibration of power quality analyzers and the measurement schema for the real grid waveforms are also depicted here.

This paper describes the design of a measurement system for supraharmonic emissions in the frequency range of 2 to 150 kHz, and analyzes the measurements obtained in real grid scenarios. The measurement system is first characterized in the laboratory. The Design of Experiment approach then uses an adequate number of experiments to identify the effects and interactions of factors responsible for supraharmonic emissions. For each of these experiments, the measured supraharmonic emissions are analyzed and quantified using the discrete Fourier transform. Next, this data is studied using the Analysis of Variance method, which enables identifying the critical factors that generate supraharmonic emissions in the network. The measurement and analysis results show the individual effects and interactions between these factors.

Wideband current transducers with a voltage output are often used to measure AC currents at frequencies up to 1 MHz. The ratio of output voltage to primary current as a function of frequency is the calibration result of these transducers. A traceable method to measure 1 A alternating current at frequencies of 100 kHz and 1 MHz is reported in this paper. The ratio of the wideband current transducer is obtained with expanded uncertainties of 1.3 % for 1 A, 100 kHz and of 2.0 % for 1 A, 1 MHz.

The understanding of high current events such as short circuit transients and impulse currents is important for the management of power quality. The work carried out and presented in this paper is focused on the characterization of commercial current transducers for on-site grade and traceable measurements of 8/20 μs (rise/fall time) impulse currents up to 60 kA peak value with a target uncertainty of 0.1 % for the complete measurement system. The investigation method consists in using two current transducers (Pearson and Rogowski coils) that will detect simultaneously the same impulse current.

Current transformers allow the measurement of high AC currents (several kA) by reducing the value of this current to normalised levels of 1 A or 5 A. They can therefore standardize current measurement equipements while providing dielectric isolation of the primary circuit. The parameter to be calibrated is a complex number representing the error on the ratio and the phase shift between the primary and secondary currents, which depends on the load of the transformer. This calibration can be done using a current comparator, and this method provides the best overall uncertainty (some 10-6 in relative value). Two current comparators with magnetic flux cancelling have been made in the 1970s by the Laboratoire Central des Industries Electriques. The first covers a range of primary current from 5 A to 1000 A, and the second from 25 A to 25000 A. They are associated with manually operated electronic equipments: an adjustable dummy load or “burden” and an injection system for the error current. In those years, the development of the electronic devices has been very difficult due to the poor performance of the components used, and the desire to achieve a closed loop controlled system for direct reading of the current error, and direct controlling of the load. These electronic devices have been entirely redefined by abandoning the idea of a servo system for direct reading, thus complicating their operation. But they are now fully controllable by a remote computer via an USB connection, allowing full automation of the procedure: there is no more manual control, either switch or potentiometer, they all have been replaced by electronic circuits. This radical modernisation also resulted in a significant reduction of the dimensions: everything fits in a single 19" × 3U standard cabinet.

Resistance standards with values in the T. range play an important role in electrical instrumentation. The calibration of such standards is, thus, a service offered by many metrology institutes. The techniques used to measure very high resistance values differ quite substantially from the calibration techniques applied in the lower resistance ranges. For this reason, the EURAMET technical committee for electricity and magnetism decided in 2008 to organise for the first time a supplementary comparison of resistance at 1 T Omega and 100 T Omega based on well characterized travelling standards.Eighteen European National Metrology Institutes participated in the comparison. With some exceptions, the results supplied by the participants agree reasonably well with the comparison reference value within the expanded uncertainty.As observed in other resistance comparisons, the characteristics of the standards used as transport artefacts ultimately limit the accuracy of comparisons in this field. The transport behaviour is difficult to model and introduces an undesired bias in the laboratory results. The transport uncertainties are at the level of the uncertainties claimed by some of the participants and, thus, limit the meaningfulness of the comparison results.Another remarkable observation is the big difference in the uncertainty statements made by the participants; even in cases there similar measurement systems were used. The results of the comparison allow the participants to critically review their measurement procedures and uncertainty models.