Error Characteristic Analysis And Optimization Strategy Research On Fiber Optic Current Transformers

The fiber optic current transformer(FOCT)has some advantages including good insulation properties and fine dynamic performance and has been a research focus.However,the actual precision problem is the main obstacle to restrict its large-scale application.Therefore,it is of great significance to analyze the effects of various internal and external factors on the FOCT precision and propose the optimization methods.First of all,from a macroscopic view,the changes of the polarization state are analyzed and the mathematical model of the FOCT output signal is built by using the Jones matrix.From a microcosmic view,the distributed parameter models of the magneto-optical effect and fiber linear birefringence are established respectively with Maxwell's equations and fiber property changes.Secondly,based on the macroscopic analysis,a mathematical model of polarization error is established.Considering the polarization error characteristics,some improving suggestions are proposed to select and install the polarization devices.Based on the microcosmic sensing analysis,the error models are set up respectively under the temperature change and vibration interference to analyze the effects of various factors on the FOCT operating precision.Some optimization suggestions are given from several aspects including the fiber type,geometric parameters,working wavelength and installation structure.Based on the error analysis,a differential magneto-optic compensation method of the FOCT is designed to compensate the fiber signal with the magneto-optical glass signal.The mathematical models of optical signals are established,the validity of which is confirmed by using COMSOL.The signal processing system is designed.The real-time signal is simulated in the LabVIEW platform,illustrating the effectiveness of the signal compensation method.Finally,the experimental platform of the FOCT based on polarization detection is designed and built.The current and error tests are performed under different extinction ratios,different polarization direction deviations and different temperature conditions.The experimental results verify the rationality of the theoretical error analysis.The magneto-optic signal is added to compensate the fiber signal.The output current is stable when the fiber signal fluctuates,which verifys the effectiveness of the signal processing method with magneto-optic compensation in the experiment.