This paper describes the setup and characterization of a set of wideband Current-to-Voltage (C-to-V) transformers equipped with symmetrical primary windings. The objective is to use the C-to-V transformer set to calibrate digital instrument transformer (IT) accurately at power frequency and within a wider frequency range to cover power quality aspects. The errors of the 50 A and the 200 A reference current transformer (CT) were within ±10 ppm and μrad at 50 Hz. The frequency responses of the two CTs up to 12 kHz were below 0.1 % and 0.2 crad.

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A unique comparison has been performed of two reference setups for the calibration of industrial power transformer loss measurement systems (TLMSs). The setups are developed by the Van Swinden Laboratorium (VSL), Delft, The Netherlands and Physikalisch-Technische Bundesanstalt (PTB), Brunswick, Germany, with the aim to calibrate industrial TLMS as a complete system, rather than just via its individual components, with an uncertainty better than 50 µW/VA, for voltages up to 100 kV, currents up to 2 kA, and power factors down to 0. The results of the comparison show excellent agreement of the PTB and VSL reference setups, both for the individual components as for the complete system. The phase agreement in the VSL and PTB component calibration results is better than (2 ± 5), (5 ± 12), and (10 ± 15) µrad for all calibration points in current ratio, voltage ratio, and power, respectively. In the full system comparison, the difference in the results of the VSL and PTB systems is less than 12 µW/VA for currents up to 1000 A and voltages up to 70 kV, with a −7 µW/VA difference averaged over all comparison measurements. This is well within the present 25 µW/VA measurement uncertainty of each of the VSL and PTB reference setups.