Protection Engineering Basics and Schemes Protection Engineering | Page 13

current is transformer only in excitation current, which in excess can damage the magnetic coupling of CT or CT.

1.1.3 Errors: There are two types of errors in CT, CT is working for current Transformation, Current is Vector quantity, Errors are typified in terms of Magnitude and Phase angle.

1.1.3.1 Types � Phase Displacement

Error

� Ratio Error Simple vector drawing of Current transformer is shown below

Phase diplacement error is the phase angle difference between primary and secondary current phases due to excitation current. Here it is represented by θ.

pg. 13