Modified GIC Estimation Using 3‐D Earth Conductivity

Abstract. Anomalous, large pipe-to-soil potentials (PSP) have been observed along a natural gas pipeline in eastern Ontario, Canada, where there is a major geological contact between the highly resistive rocks of the Precambrian Shield to the west and the more conductive Paleozoic sediments to the east. This study tested the hypothesis that large variations of PSP are related to lateral changes of Earth conductivity under the pipeline. Concurrent and co-located PSP and magnetotelluric (MT) geophysical data were acquired in the study area. Results from the MT survey were used to model PSP variations based on distributed-source transmission line theory, using a spatially-variant surface geoelectric field. Different models were built to investigate the impact of different subsurface features. Good agreement between modelled and observed PSP was reached when impedance peaks related to major changes of subsurface geological conditions were included. The large PSP could therefore be attributed to the presence of resistive intrusive bodies in the upper crust and/or boundaries between tectonic terranes. This study demonstrated that combined PSP-MT investigations are a useful tool in the identification of potential hazards caused by geomagnetically induced currents in pipelines.

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Quantitative influence of coast effect on geomagnetically induced currents in power grids: a case study

Journal of Space Weather and Space Climate ◽

10.1051/swsc/2018046 ◽

2018 ◽

Vol 8 ◽

pp. A60 ◽

Cited By ~ 11

Author(s):

Chunming Liu ◽

Xuan Wang ◽

Hongmei Wang ◽

Huilun Zhao

Keyword(s):

Three Dimensional ◽

Power Grids ◽

Normal Operation ◽

Power Networks ◽

Geomagnetically Induced Currents ◽

Coast Effect ◽

1D Model ◽

Coastal Effect ◽

Induced Currents ◽

Earth Conductivity

In recent years, several magnetic storms have disrupted the normal operation of power grids in the mid-low latitudes. Data obtained from the monitoring of geomagnetically induced currents (GIC) indicate that GIC tend to be elevated at nodes near the ocean-land interface. This paper discusses the influence of the geomagnetic coast effect on GIC in power grids based on geomagnetic data from a coastal power station on November 9, 2004. We used a three-dimensional (3D) Earth conductivity model to calculate the induced electric field using the finite element method (FEM), and compared it to a one-dimensional (1D) layered model, which could not incorporate a coastal effect. In this manner, the GIC in the Ling’ao power plant was predicted while taking the coast effect into consideration in one case and ignoring it in the other. We found that the GIC predicted by the 3D model, which took the coastal effect into consideration, showed only a 2.9% discrepancy with the recorded value, while the 1D model underestimated the GIC by 23%. Our results demonstrate that the abrupt lateral variations of Earth conductivity structures significantly influence GIC in the power grid. We can infer that high GIC may appear even at mid-low latitude areas that are subjected to the coast effect. Therefore, this effect should be taken into consideration while assessing GIC risk when power networks are located in areas with lateral shifts in Earth conductivity structures, such as the shoreline and the interfaces of different geological structures.

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EARTH CONDUCTIVITY DETERMINATIONS EMPLOYING A SINGLE SUPERCONDUCTING COIL

Geophysics ◽

10.1190/1.2035912 ◽

1976 ◽

Vol 41 (6) ◽

pp. 1184-1206 ◽

Cited By ~ 8

Author(s):

H. F. Morrison ◽

William Dolan ◽

Abhijit Dey

Keyword(s):

Large Scale ◽

Low Frequency ◽

High Sensitivity ◽

Input Resistance ◽

Measurement Sensitivity ◽

Superconducting Wires ◽

Superconducting Coil ◽

Airborne Electromagnetic ◽

Earth Conductivity ◽

Ground Conductivity

A low‐frequency airborne electromagnetic prospecting method has been developed which exploits the inherent low resistance of a superconducting coil. Changes in the input resistance of this coil are monitored in the presence of the conducting earth. The response of the system, the change in the input resistance, is proportional to the quadrature secondary magnetic field at the transmitter, although unlike two‐coil systems, the response does not decrease with increasing frequency. This research has demonstrated that superconducting wires, large scale nonmetallic cryostats, the requisite measurement circuitry, and an appropriate data acquisition system are realizable in a practical flight configuration. The unicoil presents the following significant advantages in electromagnetic prospecting: 1) The measurement sensitivity is not limited by the relative coil motion experienced by two‐coil systems. 2) Ample field strength may be supplied to override ambient noise. 3) Optimum frequencies for specific geologic sections are easily implemented in the range of 10 to 2000 Hz. 4) Maps of ground conductivity may be obtained because precise thermal stability is maintained and the measurement, therefore, is absolute. 5) The point source observation minimizes analytic complexity. 6) The combination of the foregoing features with multiple frequency operation, yields a system of potentially high sensitivity and unprecedented depth of exploration. The unicoil system also possesses some disadvantages: 1) An operational complexity results from the cryogenic procedures required in the field, and 2) the heavy sensor requires a large helicopter.

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Modeling of direct current traction power system with the consideration for earth conductivity

Transport of the Urals ◽

10.20291/1815-9400-2020-2-75-79 ◽

2020 ◽

pp. 75-79

Author(s):

Dmitriy Valentinovich Lesnikov ◽

Keyword(s):

Mathematical Model ◽

Power System ◽

Direct Current ◽

Skin Resistance ◽

Railway Network ◽

Traction Power Supply System ◽

Traction Substations ◽

Traction Power Supply ◽

Earth Conductivity ◽

Traction Power

Nowadays, one of the main tasks facing the JSC Russian Railways is the increase of volumes of freight transportation. The solution of this task is directly connected with the increase of the load on traction power system devices and their strengthening, which is primarily related to railways electrified with direct current that are characterized by high traction currents. In order to assess the possibility to strengthen a railway section and reveal «bottlenecks» in traction power supply system it is necessary to create a mathematical model of traction power system that must consider parameters of a specific section including earth conductivity that affects the values of skin resistance, potential of railway network and stray currents. The paper proposes a mathematical model of direct current traction power system that represents a combination of a catenary model and a model of railway network. The model considers parameters of traction substations, connection scheme of catenary suspensions and possible influence of rails from adjacent tracks on each other.

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Results of the August 1972 Wisconsin Test Facility effective earth conductivity measurements

Journal of Geophysical Research Atmospheres ◽

10.1029/jb079i005p00725 ◽

1974 ◽

Vol 79 (5) ◽

pp. 725-732 ◽

Cited By ~ 14

Author(s):

Peter R. Bannister ◽

Frederick J. Williams

Keyword(s):

Test Facility ◽

Conductivity Measurements ◽

Earth Conductivity

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Electromagnetic modeling of 3-D structures by the method of system iteration using integral equations

Geophysics ◽

10.1190/1.1443223 ◽

1992 ◽

Vol 57 (12) ◽

pp. 1556-1561 ◽

Cited By ~ 125

Author(s):

Zonghou Xiong

Keyword(s):

Integral Equations ◽

Three Dimensional ◽

Computation Time ◽

Iterative Solution ◽

Matrix Inversion ◽

Electromagnetic Modeling ◽

Direct Inversion ◽

Conductivity Structure ◽

The Matrix ◽

Earth Conductivity

A new approach for electromagnetic modeling of three‐dimensional (3-D) earth conductivity structures using integral equations is introduced. A conductivity structure is divided into many substructures and the integral equation governing the scattering currents within a substructure is solved by a direct matrix inversion. The influence of all other substructures are treated as external excitations and the solution for the whole structure is then found iteratively. This is mathematically equivalent to partitioning the scattering matrix into many block submatrices and solving the whole system by a block iterative method. This method reduces computer memory requirements since only one submatrix at a time needs to be stored. The diagonal submatrices that require direct inversion are defined by local scatterers only and thus are generally better conditioned than the matrix for the whole structure. The block iterative solution requires much less computation time than direct matrix inversion or conventional point iterative methods as the convergence depends on the number of the submatrices, not on the total number of unknowns in the solution. As the submatrices are independent of each other, this method is suitable for parallel processing.

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