Determination of Current Transformer Errors at Primary Currents up to 100 000 A

A method is described for testing precision current transformers, particularly devices with very high values of rated primary current and rated secondary currents up to 200 A. It makes use of the well-known differential method (Arnold, Hohle), substituting, however, the common resistor with an electronic operational amplifier, thus yielding an almost negligible resistance and a very high sensitivity of 0.01 ppm. Results of ratio error measurements are reported at values of primary currents between 500 and 100 000 A.