Research on digital optical fiber current transformer with CT power supply

A digital optical fiber current transformer (OCT) based on Rogowski coil and optical fiber transmission for use in high voltage systems is described in this paper. The technologies of signal sampling, processing and communication for the optical current transformer are introduced. The paper analyzes the present supply power techniques on high voltage side, and puts forward a new closed-loop regulating method through tailor-made small CT to obtain stable supply power. The experiment results verified that the designed power supply can operate normally as the current of bus is above 8A. The accuracy of current measurement is 0.2%.