A new current comparator-based self-calibrating instrument for current transformer calibration has been developed. The instrument measures the in-phase and quadrature components of the error by means of a digital vector voltmeter. The built-in ratio matching unit makes it possible to compare current transformers of different ratios. A set of built-in auxiliary windings ensure complete on-site self-testing of the instrument. The ratio matching unit can be tested and calibrated by the anti-offset method. The basic accuracy of the instrument is 2 ppm with 0.1 ppm resolution.
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