Effect Of Conductivity Lateral Change On Induced Geo-electric Field During Magnetic Storms

During magnetic storms, the induced geoelectric field drives geomagnetically induced currents (GIC) in power transmission networks, railway systems and pipelines, which have negative effect on those systems. The calculation of geoelectric field is an important step in the evaluation of GIC. And the earth electrical structure is an influence factors of geoelectric field. In the region with complex geological structure, the lateral change of earth conductivity can cause severe distortion of the induced geoelectric field distribution. The "H polarisation" and the "E polarisation" are two cases of the influence of lateral change of earth conductivity. The coast effect is a typical distortion of geoelectric field in the "H polarization" case. Therefore, figuring out the relationship between conductivity lateral change and GIC is significant for accurately calculating GIC in power systems.Based on the effect characteristics of conductivity lateral change, the earth model with lateral conductivity change is established. This paper uses the finite element method to solve the boundary problem of the induced telluric current field. The electric field distribution of "E polarization" and "H polarization" is calculated. Thus the relationship between conductivity lateral change and electric field distortion is discussed based on the numerical results. The result shows that the distortion in thin sheet model is more severe.Additionally, this paper also discusses the variation of GIC in the power grid due to the lateral conductivity change. The GIC influence factors which including conductivity,frequency and the distance are discussed. The result shows that the "E polarization" can influence the GIC of power line whin 250km, the "H polarization" can inflence the GIC whin 100km. The analysis of the influence scope can provide a reference for the GIC evaluation of large scale power grid. The method and the results are significant for understanding the influence of the lateral changes of conductivity and the accurately calculating of GIC.