Sensing Mechanism Under Non-Uniform Magnetic Field And Anti-Magnetic Technology Of MOCT

In modern power system,the widespread application of HVDC and GIS intelligent substation,the construction of strong smart grid and Ubiquitous Power Internet of Things put forward higher requirements for current transformer.As a new passive electronic current transformer,straight-through magneto-optic glass optical current transformer(MOCT)has the advantages of simple structure,high integration and fast measurement speed.However,its vulnerability to non-uniform magnetic field and external current electromagnetic field interference limits its large-scale application in engineering.Therefore,in view of the above problems,the mechanism and characteristics of MOCT are analyzed,and the corresponding technology is proposed,which is of great significance to the practical application of MOCT.Firstly,the physical structure of straight-through MOCT is introduced,and its optical sensing mechanism under nonuniform magnetic field is elaborated.The Cotton-Mouton effect is explained from macro and micro perspectives.Combining the Jones matrix model of magnetically induced birefringence in inhomogeneous magnetic field,a mathematical model of MOCT output intensity is established.Secondly,based on the sensing mechanism and output light intensity mathematical model under non-uniform magnetic field,the simulation model is established by COMSOL finite element simulation software to realize the coupling of light field and magnetic field.The mathematical model of magnetic field inhomogeneity is defined,and the characteristics of magnetic field distribution,Faraday rotation angle and output light intensity under different magnetic field inhomogeneity are analyzed.Thirdly,inspired by Ampere’s loop theorem,four magneto-optic glasses are spliced together to form a straight-through strip spliced MOCT,and the mathematical model of integrating the magnetic field intensity along the optical path is deduced.Based on the mathematical model,the influence of structural parameters on the anti-EMI characteristics of MOCT is analyzed,which provides a theoretical basis for optimizing the anti-EMI characteristics of MOCT.Finally,based on the above analysis and construction of experimental platform,a new 45° combined strip splicing MOCT technology is proposed,which has the advantages of excellent anti-external electromagnetic interference performance and easy installation in practical engineering.