Study On Opto-electronic Hybrid Current Transformer

As important equipments in electric power industry, current transformer plays a primary role for working well and calculating precisely in power supplying system. With the development of national economy, the grade of voltage of power supply is improving constantly, the systematic measurement and precision of protection demand to be improving constantly. In this case, opto-electronic hybrid current transformer gradually become a hot research, which is a new type of integrated electronic current transformer basing on modern electronics technology and optical technology, and it has already accepted by electric power engineering for its attractive characteristics of high accuracy, high reliability and wide bandwidth.Papers finish encoder module in the high voltage part and the low voltage part. The low voltage part receives the digital signal from the high voltage part by fiber and changes it to analog signal. This is the method of measure current from the high voltage part. Papers simplely present the background of opto-electronic hybrid current transformer, and detailedly dissertat the principle and structure of opto-electronic hybrid current transformer. It does the analysis and design of encoder module in the high voltage part. In the low voltage part, based on All-Digital Phase-Locked Loop technology, the decoding module is designed by using the characteristic which Manchester code has rich bit timing information in itself, and it is used to collect these high speed data stream and synchronize to incoming serial data stream in order to decode the data, and then unpack the data frame and check. Via the design of decoding module this system assure the reception of the single from the high part. At the same time single chip microcomputer processes data and deposites data. The current waveform will be recovered by a D/A, which has a certain precision and without obvious distortion. This design uses VHDL language and applied CPLD. Because the CPLD has high integration and flexible programming, the real-time property and reliability of the system are ensured. Currently opto-electronic hybrid current transformer has entered a practical stage, and the application of advanced electronic and optical technology of opto-electronic hybrid current transformer is important for manufacture and application. The experiment proves that this approach is reliable and high integration. The system settles the insulation question between the high voltage and the low voltage and overcome the shortcomings of the traditional current transformer. So these provide some experience for application of electronic current transformer in substation automation system.