On-site calibration of a current transformer using a Rogowski coil

This paper describes an outdoor calibration of an instrument current transformer connected to 400 kV transmission line. The method of generation of the high current and the accuracy of calibration are discussed. The reference current measuring system consists of a current shunt, a Rogowski coil, two digitizing voltmeters and a computer to control voltmeters. The Rogowski coil is calibrated on-site with the current shunt. The output voltage of the Rogowski coil is not integrated, but it is scaled according to the on-site calibration result. Estimated uncertainties for ratio and phase displacement are less than 0,01 % and 100 μrad, respectively.