Analytical method to determine the values of current error and phase displacement of inductive current transformers during transformation of distorted currents higher harmonics
Ernest Stano, M. Kaczmarek
Abstract
The main purpose of the work is to develop the equivalent method for determine the value of current error and phase displacement of the harmonic transformation of the distorted current by the inductive current transformers (CTs). The developed analytical method allows to test the accuracy of the window type inductive CTs which are characterized by a uniform distribution of the primary and secondary windings on the surface of the magnetic core. This limitation of the applicability of the presented method excludes the possibility of a local increase in the value of the magnetic flux density in the magnetic core due to the increase number of turns in some of its sections. Another important goal of the work is to determine whether the developed analytical method allows to properly reflect the influence of the non-linearity of the magnetization characteristic of the CT’s magnetic core on the transformation accuracy of the distorted current harmonics. The developed analytical method requires to supply the secondary winding with the corresponding RMS value of the equivalent distorted voltage in order to obtain the same conditions as in the normal operating state. The measurement uncertainty of the current error and phase displacement result from the accuracy of the used measuring systems to determine the parameters of the secondary winding and to measure the secondary current and voltage as well as their phase angle at a given higher harmonic.