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Instrument transformers (ITs) are vital components of power quality (PQ) measurement systems in electrical transmission and distribution grids. Whereas measurement methods and accuracy are well defined for PQ measurement instruments, accurate knowledge about IT performance in presence of grid disturbances is missing. Main research themes of a project recently funded within the EMPIR program are described in the paper. The project focuses on the set-up of a metrological framework to enable the traceable measurement of PQ parameters when ITs are included in the measurement chains. Attention is focused on the development of reference measurement systems and the definition of IT test procedures, as well as on the quantification of the performance of ITs under realistic disturbance conditions. Moreover, an extensive characterization of voltage and current ITs will provide the basis for the identification of different sets of limits for the IT accuracy performance in PQ application and the definition of PQ accuracy classes., The research described in this Conference paper has been carried out within the 19NRM05 IT4PQ, which has received funding from the EMPIR programme co-financed by the Participating States and from the European Union's Horizon 2020 research andinnovation programme." Funder name: European Metrology Programme for Innovation and Research (EMPIR) Funder ID: 10.13039/100014132

In order to respond to a new industrial need, LNE (National Laboratory of Metrology in France) has developed a new reference system for the precise calibration of combined high voltage and high current sensors at 50 Hz and 60 Hz. The output voltages of these sensors are very low; the lowest measurable voltage is 100 µV. The phase shift between the output and the input could take any value from 0° to ± 180°. Existing commercial methods are able to perform measurement of scale factors and phase-shifts but for higher output voltages. For example for voltage transformers calibrations, the output voltage is usually greater than several volts but the phase shift is usually next to zero. New Fully automated method has been proposed and developed. The calibration of the combined transformers is performed in controlled temperature chamber by comparison to a standard current transformers and a standard voltage transformer. The output voltages coming from the combined transformer and the standards are sampled using two sampling voltmeters. The samplers are processed by a DFT algorithm allowing the possibility to have access to the amplitude and the phase of the fundamental components. The uncertainties of measurement are 0,5% for the scale factor and 0,5 mrad for the phase shift when the output voltage is equal to 100 µV. They are better than 0,01% for the scale factor and 0,01 mrad for the phase shift when the output voltages are equal to 10 mV.

Author's Accepted Version of a paper accepted for presentation in the 21st International Symposium on High Voltage Engineering (ISH2019), Budapest, Hungary, August 26-30, 2019., The work reported here has received support from the EMPIR programme co-financed by the Participating States and from the European Union's Horizon 2020 research and innovation programme.

Two compensated current comparators with magnetic flux cancelling have been made in the 1970s by the LCIE (Laboratoire Central des Industries Electriques) as a reference for high current transformers calibration for currents up to 50 kA at industrial frequencies 50 Hz, 60 Hz and 400 Hz. They are associated with manually operated electronic equipments: an adjustable phantom burden and a ratio error set capable to provide with high accuracy the quadrature and the in-phase components of the current transformer errors. This article presents the work that has been done to entirely redefine theses devices by abandoning the idea of a direct servo system of the old equipment and replacing it by a software servo that offers high calibration stability, better incertainties and fully controllable by a remote computer via an USB connection, allowing full automation of the procedure.