Characteristic Analysis And Error Mechanism Of All-fiber Current Transformers

In recent years, with the rapid development of the power system, the requirement of the transformer is more and more high. The shortcomings of traditional current transformer in practical operation have been unable to meet the needs of the application of high voltage and large current in modern power grid. And the fiber optical current transformer has the advantages of small volume, light weight, high measurement accuracy, which will become the trend of the development of mutual inductor in the future. At present, there is little research on the characteristics of fiber optical current transformer. Therefore, it has very important significance to study and master the characteristics and influence of the development of fiber optical current transformer and its popularization and application.Firstly, it reviews the basic principle, type, and performance of the optical current transformer and analyzes the advantages of various types of current transformer. At the same time, establishing experimental platform and testing temperature, noise and harmonic characteristics of fiber optical current transformer and getting the specific test data with the help of Electric Power Research Institute, Guizhou Power Grid Co., Ltd.Secondly, it generalizes the system structure of fiber optical current transformer, gives the matrix representation Jones of optical system of fiber optical current transformer. Then studying the influence of the environmental temperature which on the measuring accuracy of fiber optical current transformer, and research environmental temperature and temperature compensation through the related experiment. Finally we get the conclusion that environmental temperature has little effect on the whole optical fiber current transformer and as the temperature changes, the measurement error of the all fiber current transformer is in the range of allowable.Thirdly, it summarizes the sources, characterization of fiber optical current transformer, and analyzes basic theory and mechanism of error of white noise of fiber optical current transformer. Then we researched the data in time-domain and frequency-domain and compared under different primary input current. The result indicates that white noise in fiber optical current transformer accords with a normal distribution with mean zero, and the noise magnitude is independent of the primary current value.Finally, it deduces the transfer function of the fiber optical current transformer system which is determined to be typical of a first-order inertial system. The model is derived and simulated for the numerical average of fiber optical current transformer. Then we get the conclusion that the average time value is smaller, the smaller the impact on system bandwidth, finally, we use the fiber optical current transformer prototype test and harmonic frequency characteristics of the test data to verify the correctness of the conclusions.