Study Of Control System Of Optical Current Transformer

With the increasing requirement of stability and reliability of power system, power distribution and using system are required to be fully automotive and intelligent in measuring, monitoring and controlling. Traditional current transformer, more and more defects will be exposed, as the requirement of high quality measuring instruments in power system is increasing. Hereby, current transmitter based on photoelectric technology is researched and is named electronic current transformer or optical current transformer.Based on the deep research of IEC-60048, a optical current transformer is designed in this thesis. The principle of control system in the current transformer is: The Bus current signal is converted into voltage signal by the Rogowski coil, then it is transferred to the A/D device after the fore treatment. The converted digital signal is CRC computed and Manchester code through MCU control. It is passed to the low pressure side. The algorithm computing and waveform restore in merging Unit is finished after it is decoded.This thesis analyses the performance of Rogowski coil, and calculates electrical parameters of coil based on the formulas of electrical parameters. Then, the equivalent circuit of Rogowski coil and integrating device is simulated through MatLab to obtain the parameter of integrating device. In this thesis, the FPGA is used for the control of A/D on the high voltage side,CRC,Manchester and the circuit of low voltage side. This enhances not only the reliability of the high voltage side ,but also meets the need of optical current transformer for future power system .Three main performances of high voltage side are also analyzed in this thesis and how to design the circuit by considering these three important parameters is presented. At last, the design of control system of optical current transformer is researched and presented. Because of great flexibility, the arithmetic can be added in the circuit or this circuit can be modified according to the concrete condition of power system.