Review of Measuring Methods, Setups and Conditions for Evaluation of the Inductive Instrument Transformers Accuracy for Transformation of Distorted Waveforms

Abstract

In this review article, ideas for the development of measuring methods and setups to test inductive instrument transformer accuracy for the transformation of distorted current or voltage are analyzed. This article proposes limiting values for ratio error and phase displacement at harmonics. Moreover, the manuscript discusses some remarks about the required test waveform of voltage and current, as well as the operating conditions of the inductive instrument transformer during the test. This includes designation of the number of harmonics, their RMS values and phase angles in relation to the fundamental component, as well as the required load of the VT’s and CT’s secondary winding. The aim of this work is also to show the common requirements and principles of developed methods and measuring setups to justify the proposed solution.

Characterization of Instrument Transformers under Realistic Conditions: Impact of Single and Combined Influence Quantities on Their Wideband Behavior

“…As for the present research on ITs, it is highly developed and up to date [ 12 ]. For example, the calibration of VTs/CTs, digital ITs, and non-conventional ITs is treated in many papers [ 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 ].…”

The Reference Wideband Inductive Current Transformer

“…In accordance with the standard IEC 61869-1, the tests on harmonics should be performed with the rated primary signal at the rated frequency plus a percentage of the rated primary signal at each considered harmonic frequency [1]. There are appropriate supplying systems for such tests [3][4][5][6][7][8]. In the already published standards there are no defined requirements for the reference source.…”

“…The articles [7][8][9][10][11] demonstrate the measurement systems to assess the values of voltage error and phase displacement in VTs for the transformation of distorted voltage harmonics. The reference source is the wideband voltage divider [10,[12][13][14].…”

“…In the case of the inductive VTs, the step-up voltage transformer must be utilized in order to ensure required for tests rated at primary voltage. This is obligatory due to the nonlinearity of the magnetization characteristics of their magnetic core [7,8]. In the case of the wideband accuracy tests of the inductive CTs, due to the same reason, it is also important to ensure the appropriate values of distorted primary current to properly assess the possible levels of the self-generated low-order higher harmonics [8,15].…”

“…In the case of the wideband accuracy tests of the inductive CTs, due to the same reason, it is also important to ensure the appropriate values of distorted primary current to properly assess the possible levels of the self-generated low-order higher harmonics [8,15]. Such conditions to test the window type inductive CTs may be obtained in the rated ampere-turns conditions [7,16,17]. In the other case, in the papers [18], the solution is presented that enables the generation of distorted currents with RMS values up to 1000 A and a 10% level of higher harmonics.…”