Analysis of the Functional Mechanism of the Interference Magnetic Field on Straight Light Path Type Optical Current Transformers

The straight light path type OCTs feature simple optical paths and high reliability, but are vulnerable to interference from the external magnetic field. In this paper, the method of Jones matrix is adopted to establish the sensing models of the straight light path type OCTs for analyzing their sensing characteristics and thus revealing the functional mechanism of the interference magnetic field. It is found from the analysis that the interference magnetic field works either by changing the sensing coefficient of the straight light path type OCT or by changing the target magnetic field, moreover, the analysis also shows that the impact of the interference magnetic field on the sensing coefficient can be neglected, but the impact is significantly seen on the target magnetic field, which thus can significantly reduce the measurement accuracy of the straight light path type OCTs. The simulation results show that, under the action of 1000A interference current, the measurement error of the straight light path type OCTs is 2.91%, which is far beyond the accuracy level limit of 0.2, so the simulation results coincide with the theoretical analysis. The research in this paper can lay the theoretical basis for analyzing and optimizing the magnetic resistance characteristics of the straight light path type OCTs.