Compensation of Current Transformers’ Nonlinearities by Tensor Linearization

With the proliferation of harmonic sources in power systems, current transformers (CTs), which are the most widely used current transducers in power systems, will have to measure and monitor signals with increasing levels of distortion. The accuracy of the measurement can be affected by the nonlinear response of the CT, which is dependent on the distortion in the measured signal, but nonlinear mathematical models can be used to compensate the measured value. In this paper, the complex ratio of the CT is modeled using a frequency domain model based on tensor linearization, obtaining a real-valued compensation matrix. An accurate measurement setup has been built to characterize the CTs performance in distorted conditions. Experimental results using the proposed compensation technique are presented and discussed for two commercial CTs of accuracy class 0.5 and 1. It is demonstrated that the proposed technique can accurately reconstruct the harmonic components (up to several kilohertz) of the CT primary current from the measured CT distorted secondary current.