Study On The Optical Current Transformer With Low Power Consumption

As an important equipment of protection and electric energy measurement in Power system, current transformer plays a primary role in the safety, stability and more economical operation of power system. With the development of economy and the incessant improvement of transmission capacitance and rated voltage in power system, the conventional magnetic transformer has several shortcomings and has been difficultly to meet the need of network development that towards automation and digitized direction. In this case, considerable interest has been paid to the electronic transformers. Optical current transformer, with high security as a result of good performance, low manufacturing costs, efficiently operation and high precision, small size, light weight and low maintenance costs, has become a hot spot at home and abroad.In the beginning, the paper introduces the development of electronic transformer in and abroad, as well as the basic structure and working principle. Because of the difficulty of energy supply for the high side of electronic transformer in the study, as well as the consideration of the cost, reliability, accuracy and usefulness of design, the circuit on the high voltage part of optical current transformer based on MSP430 MCU with low power consumption was designed, which solved the energy consumption problem from the structure. The paper includes signal processing part of the hardware design, digital transformation modules and the design of optical transmission unit.Secondly, Rogowski-coil current transducer was chosen for electronic voltage/current transducer in the protection circuit, after the transmission of the digital signal through the optical fiber, the digital signal was changed back to analogy signal to realize the measurement of the current of the high voltage.Thirdly, the main function of the Signal processing part is to do some necessary transmission and procession, it includes signal integration, filtering, and some other polar transform,based on the low power consumption ,the chip was selected and the circuit was designed,the function of each part was simulated by the software OrCAD/PSpice, with the requirements of design was satisfied, the circuit was designed and improved to reach the least energy consumption. Digital conversion unit used the MSP430 MCU of TI company to realize the control, which has functional parts and low power ability. The change of different working environment helps the system to decrease the energy to the least. The software platform IAR Embedded Workbench is economical and convenient for the design and debug of the system. The software including the temperature measurement part, the A/D sampling control, CRC checksum function modules, such as Asynchronous Receiver Transmitter. The design using 16-bit micro-power high-speed A/D chip ADS8325 as the converter, and ensuring the accuracy of data acquisition, real-time and low-power system. The use of low-power, low-cost, high-performance of the MSP430 family as the control devices, reducing system power consumption to improve the performance of the controller; the optical fiber was used for the transmission between the high and low voltage side and it also worked as electrical isolation, which improved the anti-jamming ability of the signal transmission, the circuit of a low-power fiber-optic firing driver was designed.The author checked the system from the hardware and software aspects, testing system was designed for this paper, the testing results are given and an analysis of errors is also introduced. Finally, the paper was summarized, and brings out the problems needed to be solved in the future.