Modelling of voltage transformer performance in power system harmonic frequency range

Many problems related to the voltage and current harmonics imposed in contemporary power systems are observed nowadays. The paper presents the voltage harmonic transfer capability of the voltage transformer usually used for the power quality measurement in the middle and high voltage grids. A simplified lumped parameters circuit model of the voltage transformer is proposed and verified by experimental investigations. The results obtained prove that the wide band ripples of the voltage transformer transfer characteristic can result an extra measurement errors that should be taken into account in order to achieve applicable accuracy.

I. Introduction

Levels of voltage distortions in contemporary electric power grids are tending to increase despite the fact that the maximum acceptable levels are determined by numerous regulations. Voltage distortion assessment, especially in the middle and high voltage networks is based on measurements in which voltage transformers are commonly used. The transformation ratio of the voltage transformer fed by distorted primary voltage with harmonics components higher than fundamental, can be different for high frequency components [6], [9].