Study And Design Of The Current Transduser Based On Magnetic Induction

With the acceleration of electric power industry intellectualization, automation andmarketization, there is a higher demand on the current sensor which plays an importantrole in electric energy metering and relaying protection in the power system.There aremany problems existing in the electromagnetic induction current transformers used widelyin the present, such as easy magnetic saturation, narrow frequency band, poor outputlinearity, ferromagnetic resonance, oil inflammable and explosive, bulky and difficultmaintenance and so on. As the State Grid upgrading and voltage grade is higher and higher,the problems are increasingly prominent and need to be solved urgently.Based on the above reasons, the current sensing system was studied and three differentcurrent sensor systems were designed using Hall magnetic field sensor, anisotropicmagnetoresistive magnetic field sensor and giant magnetostrictive material(GMM)respectively.Among them, two current sensing systems based on magnetic field sensorwere both developed independent sensing probe, data acquisition module, main controlmodule, display module and PC interface. Sensing probe was sealed by Permalloy andcopper foil for electromagnetic shielding,which can effectively liminated most externalelectromagnetic interference. Besides these, system software was designed to acquire andprocess the magnetic field data, which was also linear fitted and calibrated.Then the errorof test data after calibration was analyzed and the repeatability and temperature driftcharacteristics of system were studied.According to the principle and excellent magnetic field measuring characteristics ofGMM, solenoid sensing probe applied to DC current detection was researched and theparameters of the solenoid were made the detailed analysis and calculation.Based on theElectronic Speckle Pattern Interferometry (ESPI) optical principle,one optical path wasbuilt to detect magnetostrictive strain generated by GMM, then speckle interference imageswere got through the CCD camera and speckle stripe images were obtained usingsubstracting mode of ESPI software in PC. After that, the stripe spacing information wasacquired after extracting stripe space from speckle stripe image by MATLAB and thefunction relationship between measured current and stripe space was obtained after currentcalibration and the curve fitting.Finally, the current sensing system based on GMM wasvalidated and tested,besides, the test data,error and temperature characteristic were alsoanalyzed.Through analysis and comparison of the three current sensing system, the traditional.Hall current sensing technology has many advantages,such as maturetechnology, high precision, high stability and large measurement range, so it is widelyapplied in current sensing field.Anisotropic magnetoresistance and GMM,as a kind of newtechnique and new functional materials, has wide application prospect and research valuein the current measurement field. Definitely, the new current sensing scheme combiningGMM and ESPI technology also has certain feasibility and practicability.