Sampling current ratio measurement system for calibration of current transducers up to 10 kA With 5 • 10‾⁶ uncertainty

A sampling current ratio measurement system has been developed, tested, and validated for the accurate complex ratio measurement of ac current transducers. Calibrations can be performed for primary currents up to 10 kA with typical expanded uncertainties of 5 • 10‾⁶ in magnitude and 5 μrad in phase (k = 2). A unique property of the system is the use of digitizers for sampling of the secondary current signals and step-down transformers with a large number of current ratios. Therefore, the system does not require the current transducer under test to be a current transformer having a nominal ratio equal to the reference current transformer. Furthermore, it allows for the accurate calibration of a large variety of different current transformers and other types of current transducers. A bilateral comparison between VSL and NRC confirms the stated uncertainty.