High Sensitivity GMM-FBG Current Sensor

At present,optical current transformers are developing rapidly,and among them,current sensors based on Giant Magnetostrictive Material(GMM)and Fiber Bragg Grating(FBG)are widely studied because of their excellent performance and better meeting the current online monitoring requirements of power system current.In this paper,a GMM-FBG current sensor structure with high sensitivity and high measurement bandwidth is designed on the basis of studying the principle of magnetostrictive material fiber grating current transformer.The specific work is as follows:In-depth analysis of the working principle of the current sensor of giant magnetostrictive material and fiber grating,on this basis,combined with the sensing characteristics of fiber grating,magnetic response characteristics and strain characteristics of giant magnetostrictive material,a magnetically conductive loop with special structure is designed,and use Ansoft simulation software to simulate and optimize the design of the sensor magnetic circuit structure,in the case of reducing the impact of coil temperature rise on GMM and FBG,the maximum efficiency of the magnetic field generated by the driving coil is introduced into GMM,to achieve the purpose of maximum measurement sensitivity under minimum current drive.According to the pre-stress characteristics of GMM,a prestressed structure applied to GMM is designed,and the sensitivity of the sensor is further increased by applying pre-stress to GMM.In addition,the amplitude-frequency characteristics of the entire pre-stressed structure were studied.Through careful design and simulation optimization,the whole structure has a higher first-order natural frequency under the condition of significantly improving the sensitivity of the sensor.Finally,a high-sensitivity GMM-FBG current sensor was fabricated,and an experimental platform of fiber grating sensor system was constructed.The feasibility of the scheme was verified by power frequency AC test and frequency response characteristic test,and the experimental results were analyzed.We got the first order natural frequency of the sensor was 8.1kHz through the frequency response characteristic experiment,which was close to the simulation result of 7.8kHz,which proved the correctness of simulation.Therefore,the measurement bandwidth of the current mutual inductance system is 8.1kHz,which meets the demand for power frequency current measurement.