Seven European national metrology institutes and one commercial laboratory participated in this international comparison of instrument voltage transformers in the range of primary voltage from 5 kV up to 22 kV.

Two instrument voltage transformers (IVT) with transformation ratios (5 and 10) kV/100 V and 22 kV/100 V served as transfer standards. The measured quantities were the voltage ratio error and the phase displacement. The measurements were performed at a frequency of 50 Hz and with a burden of B = 1 VA at unity power factor. The errors of the transfer standards were measured with (40, 60, 80, 100 and 120)% of the rated value of the primary voltage.

By result processing it was supposed that results of individual laboratories are not correlated. The comparison reference values (CRVs) and their uncertainties were calculated as weighted means. The consistency of the CRVs was checked using the χ² test and Birge ratio. The confidence coefficient E of individual laboratories was calculated for CRVs that did not pass the Birge ratio test. Results of laboratories with E > 1.5 were not included in the calculation of the corrected CRVs.

The differences from the CRVs and their uncertainties presented in tables and graphs are the results of the comparison. The good results of this comparison prove the good calibration capabilities of the participants in the field of instrument transformers.

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The final report has been peer-reviewed and approved for publication by EUROMET, according to the provisions of the Mutual Recognition Arrangement (MRA).