Operation of voltage transformer in grids with distorted signals

Abstract

Abstract. Non-sinusoidal currents and voltages caused by nonlinear loads appear in power grids more and more frequently. Determination of the voltage transformer accuracy in such conditions makes a problem. Firstly, due to lack of definition of errors for distorted signals and secondly, typical measurement bridges do not accept higher harmonics. In the paper, the new definition of transformation error for distorted voltages has been proposed and some measurement results have been presented.

Estimation of the inductive current transformer derating for operation with distorted currents

“…The evaluation of a tested CT's metrological properties for transformation of distorted currents is made on the basis of composite error defined in the IEC 60044-1 standard for current transformers [6][7]9]:…”

“…In these conditions and for transients inductive instrument transformers are characterized by significantly worst metrological properties than at rated frequency of sinusoidal primary signal [1][2][3][4][5][6][7]. The increase of transformation error for distorted voltage/current will increase the error of indirect measurements of power and electric energy.…”

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

“…These devices due to increased error of higher harmonics transformation are often characterized by lower accuracy for distorted signals than for sinusoidal signal of frequency 50 Hz (60 Hz) [1][2][3][4]. Nonetheless, normative references do not define a method to determine the accuracy of transformation of distorted signals by inductive instrument transformers [5,6].…”