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

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Bo Dong ◽  
Zezhong Wang ◽  
Risto Pirjola ◽  
Chunming Liu ◽  
Lianguang Liu
Keyword(s):  
Power Systems ◽  
Electric Fields ◽  
Three Dimensional ◽  
Geoelectric Field ◽  
Geomagnetically Induced Currents ◽  
Geomagnetic Disturbances ◽  
Planar Grid ◽  
Induced Currents ◽  
Telluric Currents ◽  
Earth Conductivity

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.

scholarly journals Induced currents due to 3D ground conductivity play a major role in the interpretation of geomagnetic variations

2020 ◽  
Vol 38 (5) ◽  
pp. 983-998
Author(s):  
Liisa Juusola ◽  
Heikki Vanhamäki ◽  
Ari Viljanen ◽  
Maxim Smirnov
Keyword(s):  
Magnetic Field ◽  
Electric Fields ◽  
Time Derivative ◽  
Three Dimensional ◽  
Geomagnetically Induced Currents ◽  
Ionospheric Currents ◽  
Geomagnetic Variations ◽  
Near Surface ◽  
Induced Currents ◽  
Telluric Currents

Abstract. Geomagnetically induced currents (GICs) are directly described by ground electric fields, but estimating them is time-consuming and requires knowledge of the ionospheric currents and the three-dimensional (3D) distribution of the electrical conductivity of the Earth. The time derivative of the horizontal component of the ground magnetic field (dH∕dt) is closely related to the electric field via Faraday's law and provides a convenient proxy for the GIC risk. However, forecasting dH∕dt still remains a challenge. We use 25 years of 10 s data from the northern European International Monitor for Auroral Geomagnetic Effects (IMAGE) magnetometer network to show that part of this problem stems from the fact that, instead of the primary ionospheric currents, the measured dH∕dt is dominated by the signature from the secondary induced telluric currents at nearly all IMAGE stations. The largest effects due to telluric currents occur at coastal sites close to high-conducting ocean water and close to near-surface conductivity anomalies. The secondary magnetic field contribution to the total field is a few tens of percent, in accordance with earlier studies. Our results have been derived using IMAGE data and are thus only valid for the stations involved. However, it is likely that the main principle also applies to other areas. Consequently, it is recommended that the field separation into internal (telluric) and external (ionospheric and magnetospheric) parts is performed whenever feasible (i.e., a dense observation network is available).

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

2018 ◽  
Vol 8 ◽  
pp. A60 ◽  
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.

scholarly journals Induced telluric currents play a major role in the interpretation of geomagnetic variations

2020 ◽  
Author(s):  
Liisa Juusola ◽  
Heikki Vanhamäki ◽  
Ari Viljanen ◽  
Maxim Smirnov
Keyword(s):  
Magnetic Field ◽  
Electric Fields ◽  
Time Derivative ◽  
Three Dimensional ◽  
Image Data ◽  
Geomagnetically Induced Currents ◽  
Ionospheric Currents ◽  
Geomagnetic Variations ◽  
Near Surface ◽  
Telluric Currents

Abstract. Geomagnetically induced currents (GIC) are directly described by ground electric fields, but estimating them is time-consuming and requires knowledge of the ionospheric currents as well as the three-dimensional distribution of the electrical conductivity of the Earth. The time derivative of the horizontal component of the ground magnetic field (dH/dt) is closely related to the electric field via Faraday's law, and provides a convenient proxy for the GIC risk. However, forecasting dH/dt still remains a challenge. We use 25 years of 10 s data from the North European International Monitor for Auroral Geomagnetic Effects (IMAGE) magnetometer network to show that part of this problem stems from the fact that instead of the primary ionospheric currents, the measured dH/dt is dominated by the signature from the secondary induced telluric currents nearly at all IMAGE stations. The largest effects due to telluric currents occur at coastal sites close to highly-conducting ocean water and close to near-surface conductivity anomalies. The secondary magnetic field contribution to the total field is a few tens of percent, in accordance with earlier studies. Our results have been derived using IMAGE data and are thus only valid for the involved stations. However, it is likely that the main principle also applies to other areas. Consequently, it is recommended that the field separation into internal (telluric) and external (ionospheric and magnetospheric) parts is performed whenever feasible, i.e., a dense observation network is available.

scholarly journals Modelling geomagnetically induced currents in midlatitude Central Europe using a thin-sheet approach

2017 ◽  
Vol 35 (3) ◽  
pp. 751-761 ◽  
Author(s):  
Rachel L. Bailey ◽  
Thomas S. Halbedl ◽  
Ingrid Schattauer ◽  
Alexander Römer ◽  
Georg Achleitner ◽  
...  
Keyword(s):  
Power Systems ◽  
Geomagnetic Storms ◽  
Thin Sheet ◽  
Geoelectric Field ◽  
Geomagnetically Induced Currents ◽  
Geomagnetic Variations ◽  
Detailed Surface ◽  
Short Period ◽  
Long Time ◽  
Induced Currents

Abstract. Geomagnetically induced currents (GICs) in power systems, which can lead to transformer damage over the short and the long term, are a result of space weather events and geomagnetic variations. For a long time, only high-latitude areas were considered to be at risk from these currents, but recent studies show that considerable GICs also appear in midlatitude and equatorial countries. In this paper, we present initial results from a GIC model using a thin-sheet approach with detailed surface and subsurface conductivity models to compute the induced geoelectric field. The results are compared to measurements of direct currents in a transformer neutral and show very good agreement for short-period variations such as geomagnetic storms. Long-period signals such as quiet-day diurnal variations are not represented accurately, and we examine the cause of this misfit. The modelling of GICs from regionally varying geoelectric fields is discussed and shown to be an important factor contributing to overall model accuracy. We demonstrate that the Austrian power grid is susceptible to large GICs in the range of tens of amperes, particularly from strong geomagnetic variations in the east–west direction.

scholarly journals Comparison of methods for modelling geomagnetically induced currents

2014 ◽  
Vol 32 (9) ◽  
pp. 1177-1187 ◽  
Author(s):  
D. H. Boteler ◽  
R. J. Pirjola
Keyword(s):  
Power Systems ◽  
Transmission Lines ◽  
Matrix Method ◽  
Low Voltage ◽  
Geoelectric Field ◽  
Geomagnetically Induced Currents ◽  
Common Path ◽  
Admittance Matrix ◽  
Induced Currents ◽  
Matrix Expression

Abstract. Assessing the geomagnetic hazard to power systems requires reliable modelling of the geomagnetically induced currents (GIC) produced in the power network. This paper compares the Nodal Admittance Matrix method with the Lehtinen–Pirjola method and shows them to be mathematically equivalent. GIC calculation using the Nodal Admittance Matrix method involves three steps: (1) using the voltage sources in the lines representing the induced geoelectric field to calculate equivalent current sources and summing these to obtain the nodal current sources, (2) performing the inversion of the admittance matrix and multiplying by the nodal current sources to obtain the nodal voltages, (3) using the nodal voltages to determine the currents in the lines and in the ground connections. In the Lehtinen–Pirjola method, steps 2 and 3 of the Nodal Admittance Matrix calculation are combined into one matrix expression. This involves inversion of a more complicated matrix but yields the currents to ground directly from the nodal current sources. To calculate GIC in multiple voltage levels of a power system, it is necessary to model the connections between voltage levels, not just the transmission lines and ground connections considered in traditional GIC modelling. Where GIC flow to ground through both the high-voltage and low-voltage windings of a transformer, they share a common path through the substation grounding resistance. This has been modelled previously by including non-zero, off-diagonal elements in the earthing impedance matrix of the Lehtinen–Pirjola method. However, this situation is more easily handled in both the Nodal Admittance Matrix method and the Lehtinen–Pirjola method by introducing a node at the neutral point.

scholarly journals Earth conductivity structures and their effects on geomagnetic induction in pipelines

2007 ◽  
Vol 25 (1) ◽  
pp. 207-218 ◽  
Author(s):  
P. A. Fernberg ◽  
C. Samson ◽  
D. H. Boteler ◽  
L. Trichtchenko ◽  
P. Larocca
Keyword(s):  
Geoelectric Field ◽  
Geomagnetically Induced Currents ◽  
Geomagnetic Induction ◽  
Natural Gas Pipeline ◽  
Geological Conditions ◽  
Line Theory ◽  
Spatially Variant ◽  
Tectonic Terranes ◽  
The Impact ◽  
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.

Telluric Compensation for Pipeline Test Station Survey on the Alliance Pipeline System

2004 ◽  
Author(s):  
Lorne Carlson ◽  
Brent Dorman ◽  
Trevor Place
Keyword(s):  
Survey Data ◽  
Pipeline System ◽  
Geomagnetically Induced Currents ◽  
Close Interval ◽  
Induced Currents ◽  
Soil Measurements ◽  
Telluric Currents

Geomagnetically induced currents (GIC’s), or telluric currents, can have a profound effect on pipe-to-soil measurements during close interval and test station surveys. Previous studies have investigated how to improve close interval survey data with excellent results. This paper discusses a study on improving test station survey data collected on the Alliance pipeline system and the limitations of the methods used.

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