An International Comparison of 50-60-Hz Current-Ratio Standards at Currents up to 60000 A

An intercomparison of the ratio errors of the national power frequency current-ratio standards of the National Research Council of Canada and the Physikalisch-Technische Bundesanstalt of Germany has been carried out by means of transfer standard current transformers at ratios of 60 000 A : 5 A, 50 000 A : 5 A, 40 000 A : 5 A. Typical agreement between calibrations at both laboratories is of the order of 0.5 to 1.5 ppm. Details of the transfer standards are given.