An Opto-electric Transmission System Of Low Power Consumption For Optically Powered Electronic Current Transformer

Current transformer plays important role as a kind of high-voltage equipments in power system. It is applied in relay protection, system metering and analysis of power system. It has a close relation with the security and reliability of power system. Because the electromagnetic current transformers have series of shortcomings in power system with higher voltage and higher capacity, it is difficult to keep up with the requirement of automatic and digital system. Therefore, it is an inevitable trend to research a new kind of current transformer for high accuracy measurement such as electronic current transformer (ECT) which based on the technology of computer, communication and DSP. The problem of power supply on high-voltage terminal is one of the key points of the research of ECT.In this paper, the development of electronic current transformer at home and abroad is described, and the realized ECT power supply schemes are summarized. Based on the character of ECT which is developed in our laboratory, optical power supply and the opto-electric transmission system which has more power consumption in ECT are researched. The supply scheme which is applied and its device character come up.In this paper, an optical power supply in which supply and carrier wave can be multiplexed for high voltage ECT is designed, which include the driving, protecting and thermal-controlling circuit of high power laser, and converter on high-voltage terminal. In the case of not influencing the steady optical power-supply, the data transmission can consist of brief interruptions of the optical power-supply. The data can be picked off by a decoding circuit added to the power-conversion circuit on high-voltage terminal. Therefore, the system is simplified and the power consumption is lower. The improved circuitry driving fiber transmitter in primary converter works reliably with only a few mWs average power consumption, and the total power consumption of primary converter can be limited to only 40mW, so the output of the optical power-supply is cut down much. The experimental results show that more than 300mWs power is supplied, and data can be transmitted at baud rate as fast as 200kb/s;and the baud rate is 2Mb/s at the opposite direction. The baud rate will meet the communicating demand of the CT.