Analysis of the Current Transformer Core Saturation Impact on the Operation of the Algorithm for Emergency Control of the Power System Mode

The operation of protection algorithms and emergency control of power system modes is based on processing information about voltage levels and currents flowing through network elements. To measure these quantities electromagnetic voltage and current transformers with a closed magnetic core are widely used. Operating experience shows that under fault conditions with a large proportion of DC component, the core of the current transformers is subject to the risk of saturation. This leads to a violation of the correct operation of protection and emergency control algorithms. As a result, a loss of stability of the power system elements may occur, which, in turn, may lead to a disruption of the power system. In this paper a method for detecting saturation and restoring current of a current transformer, as well as a saturation-robust algorithm for emergency control are proposed. Computational experiments were conducted based on the mathematical model of the IEEE39 power system. Computational experiments with current transformer saturation showed that the proposed method’s average error was 4%. After integrating the method into the emergency control algorithm, the error in estimating the generator and turbine rotor acceleration energy decreased from 47.6% to 0.6%, and the error in analyzing the extreme point of the distorted measured current waveform decreased from 4 ms to 0.11 ms. This allowed the studied synchronous generator №7 to maintain stability after a fault in the power system.