Increasing the Reliablity of the Measuring Circuits of Protection Relays

Abstract

The primary current of a current transformer (CT) is calculated on the basis of the characteristics of the magnetization and the measured secondary current of the CT. This makes it possible to extend the linear range of operation of the measuring circuit of the protection and thereby increase the protection stability. The mathematical model of a current transformer and the reset algorithm for the primary and magnetization currents are described and the operation of the algorithm in different transient processes is analyzed.