An Approach to Model Earth Conductivity Structures with Lateral Changes for Calculating Induced Currents and Geoelectric Fields during Geomagnetic Disturbances

Bo Dong,Risto Pirjola,Chunming Liu,Lianguang Liu,Zezhong Wang

doi:10.1155/2015/761964

Abstract

During geomagnetic disturbances, the telluric currents which are driven by the induced electric fields will flow in conductive Earth. An approach to model the Earth conductivity structures with lateral conductivity changes for calculating geoelectric fields is presented in this paper. Numerical results, which are obtained by the Finite Element Method (FEM) with a planar grid in two-dimensional modelling and a solid grid in three-dimensional modelling, are compared, and the flow of induced telluric currents in different conductivity regions is demonstrated. Then a three-dimensional conductivity structure is modelled and the induced currents in different depths and the geoelectric field at the Earth’s surface are shown. The geovoltages by integrating the geoelectric field along specific paths can be obtained, which are very important regarding calculations of geomagnetically induced currents (GIC) in ground-based technical networks, such as power systems.

Highlights

During geomagnetic disturbances (GMD), geomagnetically induced currents (GIC) driven by the geoelectric field are flowing in ground-based electrical systems such as electric power transmission networks with neutral grounded transformers
The geoelectric field is the key factor for determining the GIC in power systems, and it can be determined when the sources of the GMD and the Earth conductivity structure are known
The questions arise of how to model and calculate the geoelectric field more accurately and what the exact effects of lateral conductivity variations are on geoelectric fields, on currents flowing within the Earth, and on GIC

Summary

Introduction

During geomagnetic disturbances (GMD), geomagnetically induced currents (GIC) driven by the geoelectric field are flowing in ground-based electrical systems such as electric power transmission networks with neutral grounded transformers. The geoelectric field is the key factor for determining the GIC in power systems, and it can be determined when the sources of the GMD and the Earth conductivity structure are known. In the real world, the complexities of ionospheric-magnetospheric source current systems and the inhomogeneities in the Earth’s conductivity structure make the geoelectric field nonuniform [3]. Many techniques are used for determining the geoelectric fields and the methods assume different distributions of the source currents and different conductivity structures [4]. Forward modelling of geomagnetic induction in the Earth introduces many numerical methods and modelling techniques which are good references for research of GMD effects on power systems as well [6]

Results

Discussion

Conclusion