Medium-Voltage Instrument Transformers Calibration up to 150 kHz: Methods, Reference Systems, and Comparison of Performance

Abstract

This article presents a European interlaboratory comparison of measurement systems and calibration procedures for the wideband characterization of instrument transformers (ITs) for medium voltage (MV) grids up to 150 kHz. The work, developed within the European Partnership on Metrology project 22NRM06 ADMIT, describes various voltage and current new-generation architectures and associated reference measurement systems specifically designed for the characterization of voltage transformers (VTs) and current transformers (CTs) under distorted operating conditions. A harmonized experimental protocol is applied to evaluate the scale factor (SF) and phase displacement of representative commercial ITs at power frequency and in the 9–150 kHz range. The comparison shows strong agreement among laboratories at 50 Hz and generally consistent trends up to approximately 20–30 kHz, whereas increasing, but acceptable, deviations emerge at higher frequencies because of bandwidth limitations, traveling standard behavior, and setup-dependent parasitic effects. The results provide quantitative insight into the comparability and uncertainty of the proposed approaches and highlight the main metrological challenges affecting traceable and reproducible wideband IT characterization at voltage and current levels typical of MV grids. The work contributes to the development of a harmonized metrological infrastructure for future calibration activities and standardization in the supraharmonic frequency range.