Verifica della linearità dello shunt per forti correnti di corto circuito fino a 230 kA

This technical report describes the study of the linearity of the measurement system used at INRiM for the calibration of short-circuit currents. The verification was carried out by comparison with an intrinsically linear measurement system based on a Rogowski coil. The characteristics of the INRiM measurement system are reported, particularly those of the shunt, as well as a description of the measurement system used to verify the linearity of the INRiM system. The comparative measurements between the systems are analyzed, assessing the linearity of the INRiM system both for the peak current and for the Joule integral, along with the uncertainties of these assessments. Finally, the overall uncertainties of the INRiM system were reviewed up to 170 kA and up to 230 kA, resulting respectively 4.2×10⁻³ and 5.6×10⁻³ while the uncertainty of the Joule integral increases to 3.4×10⁻². As a result of the work carried out, it is considered feasible to extend the INRiM CMC for the calibration of short-circuit currents up to 230 kA with the obtained uncertainties.