A Different Algorithm for Correcting Secondary Current of Current Transformer

Abstract

This work is about the negative effects of protection devices during current transformer (CT) saturation because the performance of the protection devices such as differential and impedance relays is mainly based on the operating condition of the CTs. Distorted secondary currents due to CT saturation depending on the magnitude of the fault current and a remnant flux in the iron core can cause misoperation or operating time delay of protective relays. Therefore, protective relay engineers have to take account of the CT saturation problem when they design a protective relay, especially such as current differential relay. The objective of this paper is to propose a simple and effective algorithm based on fast Fourier transform (FFT) for correcting secondary current of CT under saturation.