Abstract
AbstractThe induced geoelectric fields and telluric currents generated during geomagnetic storms will be distorted by lateral variations of the Earth conductivity. The Galerkin finite element method (FEM) is a useful tool to analyze complicated electromagnetic field problems. In this paper, a uniform thin sheet current with infinite width located at 100 km above the Earth's surface is assumed to represent the source of geomagnetic variations. It is harmonic with the amplitude of 1 A/m at different frequencies. Three Earth conductivity structures are modelled where the basic model is horizontally uniform for comparisons. The second and third structures have the same exact thicknesses and conductivity values with the basic one on one side and five times greater or lower values on the other side to represent conductivity variation from low to high and from high to low. The computational results show that the abrupt changes of conductivities have influences on the induced telluric currents, which can be classified as the proximity effect and the skin effect. For GIC research in power systems, especially in systems located at coastal areas, the geoelectric field and GIC should be determined taking the directions of the transmission lines and of the coast into consideration. Both the proximity effect and the skin effect should be considered along with the coast effect in research of GIC impacts during geomagnetic disturbances. Boundary conditions discussed in this paper can be varied depending on different modelling techniques and on the scales of conductivity structure models.
Published Version
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