A practical approach to evaluation of accuracy of inductive current transformer for transformation of distorted current higher harmonics

• CT maximum current error and phase displacement are determined for current harmonics.
• Composite error is used for evaluation of CT accuracy for distorted current.
• Methodology for determine optimum range of load for transformation of harmonics.
• Multiple harmonics are used for CT characterization in the presents of distortion.
• Developed pre-selection procedure enable reduction of measurement time and its cost.

In this paper the concept is discussed for evaluation of accuracy of inductive current transformer (CT) for transformation of distorted current higher harmonics. In proposed method the composite error (transformer correction factor) is determined for various operating conditions of tested CT in respect of primary currents rms value, distortion and secondary winding load active power. In this practical approach distorted primary current generated for the tests contains multiple harmonics. The results of FFT analysis of measured composite error are used to simultaneously evaluate tested CT maximum current error and phase displacement of transformation for each of the distorted current harmonic. This enables reduction of both examination time and its cost. The usage of measured differentially composite error, for evaluation of accuracy of inductive CT for transformation of distorted current higher harmonics, ensures high accuracy of obtained results, at low costs of required measuring apparatus. Presented methodology, allows determination of the optimum range of tested CT's secondary winding load, at which it can be used for transformation of distorted currents with maximum accuracy.