Analysis Of Magnetic Field Interference Characteristics Of Stacked MOCT And Elimination Of Measurement Error

In order to realize the integration and compactness of modern power grid,the old current transformer based on electromagnetic induction principle is not competent.The magneto-optical glass optical current transformer(MOCT)can obviously save space cost,and can be easily installed with primary equipment.At present,MOCT has two kinds of structures.Due to the change of the propagation direction of the optical path,the closed optical path MOCT has low stability and overall light intensity attenuation.The straight through optical path MOCT has the problems of large measurement error and easy to be affected by external magnetic interference.Therefore,this paper comprehensively considers the advantages and problems of the two types of structures,optimizes the magneto-optical sensing structure,analyzes the sensing mechanism of the proposed stacked MOCT,and explores the elimination method of magnetic interference error.Firstly,based on Biot Savart law,the calculation formula of magnetic field intensity of finite length conductor in MOCT is derived,and the axial and radial analysis of magnetic field intensity distribution of finite length conductor in MOCT is carried out.The three-dimensional model of non-uniform magnetic field in the space of finite length conductor is established,and the correctness of the theoretical derivation is verified through the calculation of COMSOL multiphysics finite element simulation software.Secondly,according to the optical sensing mechanism of stacked MOCT,the integration process of magnetic field intensity along the optical path without external magnetic field interference and considering adjacent phase magnetic field interference is analyzed,and the influencing factors of measurement error of stacked MOCT are explored.The measurement error is determined by the structure parameters and magnetic field parameters,and a complete mathematical model of stacked MOCT optical sensing is established.Thirdly,the relationship between the measurement relative error and the structure parameters of stacked MOCT,including the length of a and B segments of magneto-optical glass,is analyzed;the relationship between the measurement relative error and the magnetic field parameters of stacked MOCT,including the interference source distance and the installation angle,is analyzed;the Optical Electro Magnetic three-dimensional multi physical field coupling model of stacked MOCT is established,and the anti-magnetic interference characteristics of stacked MOCT are verified by simulation.Considering the good convergence of measurement error related nonlinear equations,this paper proposes a stacking MOCT measurement error elimination method based on Newton iterative method,and verifies that this method can effectively eliminate the error caused by external magnetic field interference.Finally,the stack MOCT measurement platform is built,and the NI data acquisition and analysis software is used to write the data analysis program;the stack MOCT measurement error elimination experiment is carried out,and the current measurement results with or without external magnetic interference are analyzed,which verifies the effectiveness of the measurement error elimination method.