Design On Differential Optical Fiber Interferometer High Voltage Current Sensor

In allusion to defects of measuring and moniting big current using electromagnetic current transformer in electric power system at present, the article designed a differential optical fiber interferometer high voltage current sensor. Compared with the projects of Faraday magnetooptical effe鑤 optical fiber current sensor and hibrid optical fiber current sensor, the system avoids the difficulties of getting electric source in high voltage side and solving temperature affect of optical fiber characteristic. Rogowski coil transforms the high voltage current into low one which modulates optical fiber enwinding on PZT, and than differential optical fiber interferometer detects phase variety. The system is simple in structure, has big measuring range and is free of affect of slow variety such as temperature. As the first sensor Rogowski coil transformed current into low voltage, which was added on PZT to modulate optical phase. Rogowski coil is simple in structure, no need electric power, and has no magnetic saturate. The article educed math models of Rogowski coil and PZT respectively, then got math model of sensor head, analyzed its noise at the same time, and tested the, sensor head structure of Rogowski coil connecting PZT has good measuring linearity. Optical phase detect need great linear extent, and orthconjugate interferometer. Based on differential interferometer theory, the article designed interferometer structure using in this system, which can compress phase till hundreds of times, extends the range of dynamic measurement; 3 X 3 optical coupler can realizes orthoconjugate interferometer, simples optical circuit structure. The article educed its math model, designed two differential optical fiber interferometer, and introduced the using of differential optical fiber interferometer in three-phase current measurement. For detecting of light power, the article designed pre-amplify circuit, analyzed it in detail, gave the principles of selection. Based on the demand of differential optical fiber interferometer structure, the article designed band-pass filter circuit and integral circuit. In the end of this article, correctness of all principles and design was proved, and the result of experiment and pefformance parameter of system was given.