| Electric Power is one of the most universal energy in our world. It is easy to obtain, transport, storage and use for electricity energy, which is hub of interaction of energy and the human activity today. Especially with smart grid developing, measuring and controlling of the power grid is put forward higher requirements, so the high voltage large current measuring will face severe challenge than that of any time before. The fiber optic current sensor (FOCS) exploiting Faraday Effect and Ampere’s Law, which has the advantages including inherent insulation, immunity to electromagnetic interference and light weight, is a promising current sensing technology in electric power industry.This thesis summarizes the development and the status of the optic fiber current sensing technology. We have chosen the fiber optic current sensor based on polarization rotated reflection interferometer (PRRI-FOCS) as the research object, for which has the more advantage in high accuracy, measuring range, the stability than other FOCS. On the basis of realizing PRRI-FOCS, particularly in order to overcome the view temperature performance and stability problems of the present optic fiber current sensor, a kind of special high birefringence spun optic fiber is designed and FOCS based on the fiber is realized. The achieved FOCS is test, which is expected to be widely used for current measuring in electric power industry.This thesis spreads out discussions around PRRI-FOCS achieving and key technology research as follows:(1) Jones vector operation was used to set up the mathematical model of light system of PRRI-FOCS, and respectively it is analyzed by using the model how to do the five kinds of process error influence the normalized sensing strength factor factors.(2) In order to achieve the PRRI-FOCS based on digital closed loop demodulation technology, whose hardware and software were designed. The signal modulation demodulation principle and modulation coefficient automatic gain compensation has been carried on the detailed introduction, which is achieved by FPGA and Verilog HDL. Finally the FOCS was achieved and the test platform for the optical fiber current sensor was set up.(3) It was analyzed by using optical system model how do temperature character is tic of the fiber wave plate (λ/4) compensate influence the sensing strength temperature deviation by Verdet constant, and it was analyzed what temperature characteristics of wave plate fiber is chosen. It is appropriate that the value of1/ρ0(dp/dt) is between in the-6×10-4℃-1and-2×10-4℃-(4) A special spun highly birefringent (HB) fiber is designed and achieved for the sensor by heating and spinning commercial linearly birefringent fiber. In contrast with conventional fibers, the fiber integrates a function of a quarter wave plate. Particularly, fabricating and working principle of the current sensor head using the fiber are expounded. The sensor achieve an accuracy with0.5%and good linearity shown in temperature dependence(a temperature driftof0.008%/℃) over a temperature range of-40℃to70℃. Further, under considering temperature compensation, the sensor accuracy is within±0.1%over in a wide range of current and temperature ranges.(5) A fiber optic current sensor based on two sensing fiber coils with different thermal performance is raised. The sensor utilizes spun panda birefringent fiber and spun elliptical-core birefringent fiber as the sensing coils. The measurement principle has been described and prototype of the sensor has been constructed. Accuracy performance (±0.2%<at rated2000A) was obtained for current measurement over a wide temperature range (-40℃-70℃). The sensor can be applied to AC/DC current measurements in the electric power industry. |
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