Simulation of the influence of conductive disturbances on accuracy of the voltage transformers during measurements of the power quality

Voltage transformers which are the source of the signals for electrical power network protection apparatus through transformation of high voltages to low voltages enables accurate measurement of high voltages and estimation of the power quality in the power network. Significant is then accuracy of the instrument transformer both in steady and transient states which means permissible values of the voltage error and the phase displacement during transfer of distorted voltages. These errors of the voltage transformers depends from the value and type of the loads of the secondary sides, frequency and value of primary voltages. Additionally, decrease of the power quality caused by nonlinear loads and conductive electromagnetic disturbances have an influence on the errors of the voltage transformer. Deterioration of the accuracy class is meaningful in honest estimation of the power quality.