Protection Engineering Basics and Schemes Protection Engineering | Page 10

I primary =( N sec

N Pri

) I secondary + I excitation

It clearly showing the primary current transformed not only in secondary current but excitation current also, our main concern is secondary current but excitation current is there, more excitation current means less secondary current which is not technically desirable. To keep magnetization or excitation current as low as possible it is common practice to use good magnetic property material for Current transformer core manufacturing, so in less magnetization current our CT will be magnetically coupled with on mounted cable / conductor.

It is schematic operational drawing of Current transformer

R P is Primary Resistance L P is primary inductance e P is primary voltage pg. 10