Calibration of Wideband Current Transformers using a Precision Power Analyzer as Comparator

A measurement system is proposed for characterizing wideband current transformers (CTs) using a precision power analyzer as a sampling current ratio bridge. This approach simplifies the setup significantly with respect to conventional, primary measurement systems, with only a limited reduction in measurement uncertainty. Initial characterisation of the measurement system shows that it is able to achieve uncertainties of less than 50 ppm and 30 μrad for CT ratio error and phase, displacement, respectively over the frequency range from 50 Hz to 5 kHz, provided a calibrated wideband reference CT is available with suitably low uncertainties. This makes the system ideal for use by NMIs and in industrial applications that do not need the ultimate accuracies achieved by primary CT calibration setups.