Structural Optimization And Temperature Characteristic Analysis Of GMM-FBG Fiber Current Sensor

Fiber optic current sensors based on Giant Magnetostrictive Material(GMM)and Fiber Bragg Grating(FBG)have been widely studied,due to its excellent performance can meet the current online monitoring requirements of current power systems,but their sensitivity and stability still need to be improved.GMM-FBG couples the measured current magnetic field through the magnetic structure.The sensitivity and linearity are related to the internal magnetic field strength and uniformity of the GMM.In addition,since FBG and the magnetostrictive coefficients of GMM are temperature sensitive,the sensitivity of the sensor's AC response is affected by the temperature.Conduct research work on the above two sensitivity related issues.Based on the analysis of the sensing characteristics of FBG,the magnetic response characteristics of GMM and the coupling characteristics of GMM,the nonlinear dynamic coupling model of GMM-FBG current sensing system under magnetic field and temperature field is proposed.According to the model,the wavelength variation of the output light of the GMM-FBG fiber sensor is obtained as a function of the measured magnetic field and temperature.The magnetic finite element analysis method is used to design the magnetic circuit structure of the asymmetric quadrilateral-plane with the guide body and increase the GMM.The unit magnetic flux density of the GMM-FBG sensitive unit is increased while ensuring the uniformity of the magnetic field in the GMM,and the sensitivity of the sensor is improved.Construct a fiber optic current sensing system experimental platform to test the AC current response of the GMM-FBG current sensor from 0 to 100 A in the temperature range of 20 to 70 °C.The experimental results show that the sensitivity of the sensor decreases with increasing temperature,and the sensitivity of the sensor decreases with the increase of the measured current.Based on the experimental data of temperature characteristics,a method of measuring the current temperature of the current sensor using FBG DC offset value and correcting the current value according to the temperature offset curve of different current values is proposed.The test result of 60 A at 40 °C shows that the feedback temperature correction method reduces the current temperature drift deviation from 4.98% to 0.18%.