The purpose of the regional comparison EUROMET.EM-K8 was to compare the scaling capabilities up to 1000 V DC of the European national metrology institutes, thus extending to Europe the evaluation of equivalence of voltage ratio measurements obtained by the comparison CCEM-K8. Twenty laboratories participated, with the Istituto Elettrotecnico Nazionale Galileo Ferraris (Torino, Italy) acting as pilot laboratory. The circulation of the travelling standard, a resistive voltage divider, started in July 1998 and ended in January 2002. The technical protocol requested the measurement of voltage ratios 1000 V/10 V and 100 V/10 V, the measurement of other ratios being optional. Nineteen laboratories reported measurements of the mandatory ratios. For these ratios, the measurement methods used are described and the process to evaluate the comparison reference value and the degrees of equivalence is reported in detail. The relative uncertainty of the comparison, given by the combination of the uncertainty of the reference value and the instability of the transfer standard, was about 0.26×10^-6 for ratio 1000 V/10 V and about 0.16×10^-6 for ratio 100 V/10 V, at 95% level of confidence. The results for the optional ratios are reported in an appendix. With some exceptions, the agreement between the results is satisfactory.

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