Development of a Compensation Scheme for a Measurement Voltage Transformer Using the Hysteresis Characteristics of a Core

Abstract

This paper describes the design, evaluation, and implementation of a compensation scheme for a measurement voltage transformer (VT) using the hysteresis characteristics of the core. The error of a VT is caused by the primary winding voltage and secondary winding voltage. The latter depends on the secondary current, whereas the former depends on the primary current, which is an aggregate of the exciting and secondary currents. The secondary current is obtained directly from the secondary voltage and is used to obtain the voltage across the secondary winding. For the primary current, the exciting current is decomposed into two components: core-loss and magnetizing currents. The magnetizing current is obtained by the flux-magnetizing current curve instead of the hysteresis loop to minimize the required loops for compensation. The core-loss current is obtained by dividing the primary induced voltage by the core-loss resistance. Finally, the estimated voltages across the primary and secondary windings are added to the measured secondary voltage for compensation. The scheme can significantly improve the accuracy of a VT. The results of the performance of compensator are shown in the experimental test. The accuracy of the measurement VT improves from 1.0C class to 0.1C class. The scheme can help to significantly reduce the required core cross section of a measurement VT in an electrical energy system.