Research on digital optics fibre current transformer

A digital optics fiber current transformer (CT) based on Rogowski coils and fiber transmission with excellent insulation to Electro-magnetic to replace a conventional open-terminal ferrous core one for use in high voltage systems is described in this paper. The Rogowski coil generates a low-level voltage signal in proportional to the differential of the primary current. A passive integrator is constructed from precision components to get the corresponding voltage signal of bus current. The technology of signal sampling, processing and communication for the current transformer is introduced. The large panel LCD screen displays the waveform, RMS value, frequency, periods and so on. At the same time the present supply power techniques at high voltage side are analyzed, and puts forward to 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% and the whole system can satisfy the demand of current measurement in power system.