Characterization of absolute phase angle in wideband current shunts at Inmetro

Abstract

This paper describes the initial stage of implementing an absolute phase measurement system for the current “cage” type shunts built at Inmetro. The phase characterization of the shunts includes phase difference measurements that allow the realization of the absolute phase using three geometrically equal shunts calibrated in DC resistance. The measurement results of three shunts are presented and analyzed in comparison with the values obtained through the lumped equivalent circuit model. The results demonstrate the high capacity of the method of determining the absolute phase of shunts that have small phase shift errors. This method allowed, for the first time, the absolute phase measurement of impedances (shunts) below 10 ohms at Inmetro. The lowest measurement error was 0.4 microradians with an expanded uncertainty of 1.4 microradians for the 10 A shunt at 54 Hz.