Large Geomagnetically Induced Currents Research Articles

Modeling GIC in the Southern South Island of Aotearoa New Zealand Using Magnetotelluric Data

AbstractMagnetotelluric (MT) impedances from 62 sites in southern South Island of Aotearoa New Zealand have been used to model geomagnetically induced currents (GIC) in four transformers during two solar storms. Induced electric fields during the storms are calculated from the MT impedances using the magnetic fields measured at the Eyrewell (EYR) geomagnetic observatory, approximately 200 km north of the study area. Calculated GIC during the sudden storm commencements (SSC) give a generally good match to GIC measured by the network operator, Transpower New Zealand. Long period GIC (periods longer than about 10,000 s) are less well modeled. Calculations based on thin‐sheet modeling, which has restrictions on the shortest period of variation which can be modeled, perform less well for the GIC associated with SSC, but are equally good, if not better, at modeling longer period GIC. Consistent underestimation of large GIC at one transformer (HWBT4) near Dunedin are likely to be the result of uncertainty in the assumed values of line, transformer, and earthing resistances. The assumption of a spatially uniform magnetic field across the study area, which is implied by use of the magnetic field measured at EYR as a basis for calculation, may also lead to incorrect calculation of GIC. For one storm use of magnetic field data from a magnetometer within the study area leads to much improved modeling of the observed GIC. This study compares modeled and measured GIC using specifically measured MT impedance data.

Occurrence of Large Geomagnetically Induced Currents Within the EPRI SUNBURST Monitoring Network

AbstractSpace weather, a natural hazard, can adversely impact human technological assets. High‐voltage electric power transmission grids constitute one of the most critical technological systems vulnerable to space weather driven geomagnetically induced currents (GICs). One of the major challenges pertaining to the study of GICs over the continental United States has been the availability of GIC measurements, which are critical for validation of geoelectric field and power flow models, for example. In this study, we analyze GIC measurements collected at 17 Electrical Power Research Institute (EPRI) SUNBURST transformer locations across the United States for which a GIC value of 10 A or greater was recorded. This data set includes 52 individual geomagnetic storms with Kp index 6 and above during the period from 2010 to 2021. The analysis confirms that there is a good correlation between the number of geomagnetic storms per year and the number of recorded GIC events. Our results also show that about 76% of the top 17 GIC events are associated with the storm main phase, while only 24% are attributed to storm sudden commencements. In addition, it is shown, for the first time, that mid‐latitude positive bays can cause large GICs over the continental United States. Finally, this study shows that the largest measured GIC event in the data set was associated with a localized intense dB/dt structure, which could be attributed to substorm activity.

Forecasting the Probability of Large Rates of Change of the Geomagnetic Field in the UK: Timescales, Horizons, and Thresholds

AbstractLarge geomagnetically induced currents (GICs) pose a risk to ground based infrastructure such as power networks. Large GICs may be induced when the rate of change of the ground magnetic field is significantly elevated. We assess the ability of three different machine learning model architectures to process the time history of the incoming solar wind and provide a probabilistic forecast as to whether the rate of change of the ground magnetic field will exceed specific high thresholds at a location in the UK. The three models tested represent feed forward, convolutional and recurrent neural networks. We find all three models are reliable and skillful, with Brier skill scores, receiver‐operating characteristic scores and precision‐recall scores of approximately 0.25, 0.95 and 0.45, respectively. When evaluated during two example magnetospheric storms we find that all scores increase significantly, indicating that the models work better during active intervals. The models perform excellently through the majority of the storms, however they do not fully capture the ground response around the initial sudden commencements. We attribute this to the use of propagated solar wind data not allowing the models notice to forecast impulsive phenomenon. Increasing the volume of solar wind data provided to the models does not produce appreciable increases in model performance, possibly due to the fixed model structures and limited training data. However, increasing the horizon of the forecast from 30 min to 3 h increases the performance of the models, presumably as the models need not be as precise about timing.

Measurements and Simulations of the Geomagnetically Induced Currents in Low‐Latitude Power Networks During Geomagnetic Storms

AbstractThe issue of geomagnetically induced currents (GICs) on large distance ground‐based conductive systems is a global space weather concern nowadays. The low‐latitude power grids are becoming more vulnerable to GICs hazards due to their increasing scale and degree of interconnection. Thus, GICs measurement and modeling in these systems is of great importance. In this study, we present an analysis of the GICs measurement at a Chinese low‐latitude substation during geomagnetic storms. The results show a rough positive correlation between the magnitude of large GIC spikes and dBH/dt spikes. We then built a physical‐based model to simulate the GICs at the low‐latitude substation during storms. It was found that the simulations capture the main active periods of the GICs during the storms with comparative strength of the measurement. This differs from the previous simulation results for high‐latitude regions conducted by Welling et al. (2017; https://doi.org/10.1002/2016SW001505). Furthermore, the event analysis method is applied to evaluate the model performance. The results indicate that the physical‐based model is more applicable than the persistence model in the prediction of GICs at low‐latitude power grids during storms.

First GIC Estimates for the Mexican Power Grid

AbstractThis contribution addresses the first assessment of the impact of geomagnetically induced currents (GIC) on the 400‐kV power grid of Mexico. As an initial approach, we modeled GIC using a uniform conductivity for the entire Mexican territory and spatially uniform geomagnetic disturbance. Power grid data were provided by the electric operator of Mexico; the geophysical data were inferred from the main features of Mexican geology. We calculate the power grid response during four geomagnetic storms from Solar Cycles 23 and 24 (i.e., 15 July 2000, 20 October 2003, 17 March 2015, and 7 September 2017), as well as during an extreme scenario (a Carrington‐like event). The results show that the Mexican power grid can be affected by three‐phase GIC ranging from 20 to 75 A during geomagnetic disturbances. According to the model, sites located in coastal areas or close to the edges of the network can experience large GIC during time intervals between 3 and 10 hr, depending on the intensity of the geomagnetic disturbance. It is an interesting result that these sites are of the major economic and strategic significance for the country. In the case of a Carrington‐like event, the power grid could be affected by GIC ranging between 25 and 150 A under a uniform 1 V/km EW geoelectric field. Such an event might produce significant distortions in the grid hardware (i.e., transformers and static VAR compensators), potentially leading to widespread damage.

Fine structure of substorm and geomagnetically induced currents

The rapid changes dB/dt of the Earth’s magnetic field due to substorms can excite large geomagnetically-induced currents (GICs) that can have harmful effects on technological systems. This paper presents an analysis of the characteristics of dB/dt enhancements observed in Fennoscandia using data from the IMAGE magnetometer chain along a geomagnetic longitude of 110 o . The abrupt geomagnetic field variations may be associated with the substorm onsets, isolated magnetic impulsive events (MIEs), and quasi-periodic series of MIEs, known as Ps6 pulsations (periods 5-15 min). For a detailed examination of the latitudinal structure of dB/dt enhancements and their association with the auroral oval boundaries we applied the technique of magnetic keograms. This simple technique helps to visualize and characterize the fine structure of substorm, namely the location in time and latitude of dB/dt enhancements. The location of the auroral oval boundaries has been estimated with the OVATION-prime model. Among the different types of impulsive disturbances investigated auroral substorm onset provides the largest GICs (few tens of A). Isolated nightside MIEs are also effective in the excitation of GICs (>10 A). Ps6 pulsations are effective in the excitation of GICs with magnitude about 20 A and even higher. Monochromatic Pc5 pulsations are capable to induce noticeable GICs, up to ~13 A. Large localized disturbances on short timescales are the actual drivers of GICs, and they may be imagined like geomagnetic “strokes” during magnetospheric “thunderstorms”.

Geomagnetically Induced Currents Caused by Interplanetary Shocks With Different Impact Angles and Speeds

AbstractThe occurrence of geomagnetically induced currents (GICs) poses serious threats to modern technological infrastructure. Large GICs result from sharp variations of the geomagnetic field (dB/dt) caused by changes of large‐scale magnetospheric and ionospheric currents. Intense dB/dt perturbations are known to occur often in high‐latitude regions as a result of storm time substorms. Magnetospheric compressions usually caused by interplanetary shocks increase the magnetopause current leading to dB/dt perturbations more evident in midlatitude to low‐latitude regions, while they increase the equatorial electrojet current leading to dB/dt perturbations in dayside equatorial regions. We investigate the effects of shock impact angles and speeds on the subsequent dB/dt perturbations with a database of 547 shocks observed at the L1 point. By adopting the threshold of dB/dt = 100 nT/min, identified as a risk factor to power systems, we find that dB/dt generally surpasses this threshold when following impacts of high‐speed and nearly frontal shocks in dayside high‐latitude locations. The same trend occurs at lower latitudes and for all nightside events but with fewer high‐risk events. Particularly, we found nine events in equatorial locations with dB/dt > 100 nT/min. All events were caused by high‐speed and nearly frontal shock impacts and were observed by stations located around noon local time. These high‐risk perturbations were caused by sudden strong and symmetric magnetospheric compressions, more effectively intensifying the equatorial electrojet current, leading to sharp dB/dt perturbations. We suggest that these results may provide insights for GIC forecasting aiming at preventing degradation of power systems due to GICs.

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

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.

Geomagnetically induced currents in Uruguay: Sensitivity to modelling parameters

According to the traditional wisdom, geomagnetically induced currents (GIC) should occur rarely at mid-to-low latitudes, but in the last decades a growing number of reports have addressed their effects on high-voltage (HV) power grids at mid-to-low latitudes. The growing trend to interconnect national power grids to meet regional integration objectives, may lead to an increase in the size of the present energy transmission networks to form a sort of super-grid at continental scale. Such a broad and heterogeneous super-grid can be exposed to the effects of large GIC if appropriate mitigation actions are not taken into consideration. In the present study, we present GIC estimates for the Uruguayan HV power grid during severe magnetic storm conditions. The GIC intensities are strongly dependent on the rate of variation of the geomagnetic field, conductivity of the ground, power grid resistances and configuration. Calculated GIC are analysed as functions of these parameters. The results show a reasonable agreement with measured data in Brazil and Argentina, thus confirming the reliability of the model. The expansion of the grid leads to a strong increase in GIC intensities in almost all substations. The power grid response to changes in ground conductivity and resistances shows similar results in a minor extent. This leads us to consider GIC as a non-negligible phenomenon in South America. Consequently, GIC must be taken into account in mid-to-low latitude power grids as well.

Geomagnetically induced currents in Europe

Statistics of geomagnetically induced currents (GIC) in the European high-voltage power grids based on 1-min geomagnetic recordings in 1996–2008 and on 1-D models of the ground conductivity have been derived in the EURISGIC project (European Risk from Geomagnetically Induced Currents). The simplified yet realistic power grid model indicates that large GIC can occur anywhere in Europe. However, geomagnetic variations are clearly larger in North Europe, so it is the likely region of significant GIC events. Additionally, there are areas in the North with especially low ground conductivities, which further tend to increase GIC. The largest modelled GIC values at single substations in 1996–2008 are about 400 A in the Nordic Countries, about 100 A in the British Isles, about 80 A in the Baltic Countries, and less than 50 A in Central and South Europe. The largest GIC event in the period studied is the Halloween storm on 29–30 October 2003, and the next largest ones occurred on 15 July 2000 and 9 November 2004.

Assessment of GIC risk due to geomagnetic sudden commencements and identification of the current systems responsible

AbstractDuring periods of enhanced geomagnetic activity, geomagnetically induced currents (GIC) flow in power systems potentially causing damage to system components or failure of the system. The largest GIC are produced when there are large rates of change of the geomagnetic field (dB/dt). It is well established that the main phase of a geomagnetic storm, particularly the magnetic substorms occurring during that period, is a cause of large GIC and hence a risk factor for power systems. However, some power system disturbances have been associated with the occurrence of a storm sudden commencement (SSC) prior to the main phase. We investigate the magnetic signature observed on the ground and the associated solar wind and interplanetary magnetic field (IMF) conditions for both SSC and sudden impulse (SI) events, which are grouped together as sudden commencements (SC). SCs are primarily attributed to a sudden enhancement of the magnetopause current. For some events, we show that there is a high‐latitude enhancement (HLE) of the SC amplitude and corresponding dB/dt. The limited spatial extent suggests an ionospheric current source. Examination of the polarity of the change in the X‐component magnetic field shows that the HLE is due to a sudden increase of the ionospheric convection electrojets. The occurrence of the HLE is more prevalent for SSC‐type SCs, SCs caused by coronal mass ejections as opposed to corotating interaction regions, and SCs associated with a large solar wind speed (vsw) prior to the SC or a large Δvsw at the time of the SC.

Geomagnetically induced currents in Norway: the northernmost high-voltage power grid in the world

We have derived comprehensive statistics of geomagnetic activity for assessing the occurrence of geomagnetically induced currents (GIC) in the Norwegian high-voltage power grid. The statistical study is based on geomagnetic recordings in 1994–2011 from which the geoelectric field can be modelled and applied to a DC description of the power grid to estimate GIC. The largest GIC up to a few 100 A in the Norwegian grid occur most likely in its southern parts. This follows primarily from the structure of the grid favouring large GIC in the south. The magnetic field has its most rapid variations on the average in the north, but during extreme geomagnetic storms they reach comparable values in the south too. The ground conductivity has also smaller values in the south, which further increases the electric field there. Additionally to results in 1994–2011, we performed a preliminary estimation of a once per 100 year event for geoelectric field by extrapolating the statistics. We found that the largest geoelectric field value would be twice the maximum in 1994–2011. Such value was actually reached on 13–14 July 1982.

Geomagnetically induced currents in Europe: Characteristics based on a local power grid model

We consider the model of the Finnish high‐voltage power grid in 1978–1979, for which the accurate parameters are available for calculating geomagnetically induced currents (GIC). Moving the grid at different locations across Europe gives estimates of GIC levels in this region. For calculating the geoelectric field driving GIC, we use different layered models of the ground conductivity and 1 min geomagnetic data of the year 2003. The results show a clear concentration of large GIC in north Europe, where the peak values are about 3–5 times larger than in Central and South Europe, being up to about 200 A in this specific power grid. There are two factors contributing to this finding. First, geomagnetic variations are generally stronger in the north. Second, there are regions in the north with clearly smaller ground conductivities than typically at other areas. Both of these reasons lead to larger electric fields in the north. A very similar behavior of GIC is found in the case when a single‐layered ground conductivity model is assumed everywhere. We also show that the geographic characteristics of GIC are quite insensitive to the details of the power grid model by modifying various parameters of the Finnish grid.

European Project to Improve Models of Geomagnetically Induced Currents

Geomagnetically induced currents (GICs) from solar storms pose a risk to the operation of power transmission grids in Europe and across the globe. The European Risk from Geomagnetically Induced Currents (EURISGIC) project, which began in March 2011 and is supported by the Seventh Framework Programme of the European Union, seeks to mitigate this natural hazard by developing European capabilities for GIC forecasting and warning. Recent well-recognized GIC events were the province-wide blackout in Quebec, Canada, in March 1989 and the blackout in the city of Malmö, in southern Sweden, during the Halloween storm of October 2003. The progressive integration of interconnected and geographically wide power transmission grids is obviously increasing the GIC risk. Hence, there is a need for greater scientific understanding of phenomena in the solar-terrestrial environment that lead to GICs and for the development of systems that facilitate GIC modeling, forecasting, and mitigation. Within the EURISGIC project the flow of GICs throughout the European grid for hypothetical and real events will be simulated using improved grid network models and conductivity models for the continent. The project will produce the first Europe-wide real-time prototype forecast service of GICs in high-voltage power systems, based on in situ solar wind observations by the Advanced Composition Explorer (ACE) spacecraft, empirical modeling, and comprehensive simulations of Earth's magnetosphere. Moreover, on the basis of long-term geomagnetic recordings, EURISGIC will derive the first map of the statistical risk of large GICs throughout Europe. Of special interest is a search for untapped data sources for the solar storm of September 1859, famously observed by British astronomer Richard Carrington, which is often referred to as the most intense geomagnetic storm ever recorded. The project aims to assist European scientists as they strive for 30- to 60-minute lead time forecasts of GIC events. There is presently only one European magnetohydrodynamic code for global simulations of the solar wind-magnetosphere interaction, namely, Grand Unified Magnetosphere-Ionosphere Coupling Simulation (GUMICS-4), developed at the Finnish Meteorological Institute. During EURISGIC, GUMICS-4 will be upgraded to be able to produce real-time GIC forecasts. For this development, EURISGIC will obtain valuable contributions from the U.S. expertise gained from NASA's Solar Shield project (http://ccmc.gsfc.nasa.gov/Solar_Shield/). The U.S. and European codes will run in parallel to produce GIC forecasts in Europe, and they will also stimulate further improvements in simulations. Calculation of GICs in a given power grid is a straightforward problem, which has been considered in several previous national studies, for example, in Finland, Sweden, and the United Kingdom. The key problem is to determine the geoelectric field that drives GICs in power grids. This electric field can be calculated from the measured magnetic field using models of the Earth's conductivity. A special challenge for EURISGIC is to compile a simplified conductivity map of Europe that enables efficient computation of Europe's electric field. When the geoelectric field is known, calculation of GICs in a power grid is reduced to a simple direct current (DC) mathematical problem. In combination, early warning forecasts, risk maps, and worst-case-scenario assessments provided by EURISGIC will contribute to mitigating the risks that GICs represent, thereby avoiding destruction of transformers and enhancing the protection of critical infrastructure in Europe and elsewhere in the world. The project began in March 2011 and will last until February 2014. The Finnish Meteorological Institute is the coordinator, with Ari Viljanen as the coordinating person. Other European Union partners come from Hungary, Sweden, and the United Kingdom. In addition, Russia and the United States belong to the consortium, ensuring the best global GIC expertise within the team. An external group of advisors representing power engineering, education, and space weather services will provide independent reviewing and suggestions to help the consortium reach its ambitious goals. EURISGIC is funded by the Seventh Framework Programme of the European Union (Project 260330). The EURISGIC Web site is http://www.eurisgic.eu. The following are members of the consortium, with their representatives given in parentheses: Finnish Meteorological Institute, Finland (Ari Viljanen); British Geological Survey/Natural Environment Research Council, United Kingdom (Alan Thomson); NeuroSpace, Sweden (Magnus Wik); Swedish Institute of Space Physics, Sweden (Peter Wintoft); Geodetic and Geophysical Research Institute, Hungary (Viktor Wesztergom); Polar Geophysical Institute, Russia (Yaroslav Sakharov); and Catholic University of America, United States (Antti Pulkkinen). Ari Viljanen is a senior scientist at the Finnish Meteorological Institute, in Helsinki, Finland. E-mail: [email protected]

Solar wind drivers of large geomagnetically induced currents during the solar cycle 23

In this paper we investigate the interplanetary drivers of the largest geomagnetically induced currents (GIC) during the solar cycle 23. Interplanetary coronal mass ejections (ICMEs) are the major causes of intense geomagnetic storms and large GIC. In particular, in this work we examine the effectiveness of different structures embedded in an ICME (namely sheath regions, ejecta, and boundary layers) in causing large GIC. It was found that when an ICME interacts with the Earth's magnetosphere the most intense GIC activity is likely to take place during the passage of the turbulent sheath region. The effectiveness of sheath regions in driving large GIC is possibly due to their capability to trigger substorms and to drive intense directly driven ionospheric activity. We also investigated the relationships between different solar wind parameters and the GIC amplitudes. The best correlation with the GIC amplitudes was found with the solar wind electric field and the epsilon parameter. Ejecta‐associated GIC seem to require an on‐going magnetospheric Dst storm while sheath regions and boundary layers can cause large GIC even when no activity is taking place in terms of Dst. Interestingly, four of the nine ejecta‐associated GIC took place during the recovery phases of a intense magnetic storm (but when Dst still was having storm time values below −50 nT).

An overview of the impulsive geomagnetic field disturbances and power grid impacts associated with the violent Sun‐Earth connection events of 29–31 October 2003 and a comparative evaluation with other contemporary storms

An overview is provided of the geomagnetic storms and impacts on electric power grids associated with the violent Sun‐Earth events of October 2003. During the period from 29 to 31 October 2003, two large geomagnetic storms were observed, as measured by periods of high Kp, Ap, and Dst indices. In fact, these storms had Ap rankings of 6th and 16th all time. This ranking would suggest that the October 2003 storms would be significant with regard to geomagnetically induced currents (GIC) in power grids. However, the resulting geomagnetic storms were much lower in delta B and dB/dt intensity than other historically large geomagnetic storms. A variety of geomagnetic storm processes drove observed GIC. For example, ground observations indicated the presence of large dB/dt pulsations and GIC at North American midlatitude locations on 29 October 2003 that may be due to unusually intense Kelvin‐Helmholtz shearing. Sustained disturbance conditions at low‐latitude and equatorial latitude locations that are likely linked to ring current intensifications may be the source of sustained GIC at these locations and the cause of large power transformer failures. Comparative evaluations will be provided for the 29–31 October 2003 storms and other important and contemporary storms, such as those observed on 13–14 March 1989, 13–14 July 1982, and 15–16 July 2001. Rather than an index‐based evaluation method, the comparative evaluations presented in this paper are based on comparisons of storm morphology. This approach provides a more meaningful comparison of geomagnetic field disturbance dynamics that are important to characterize large GIC threats to power grid infrastructures.

Fast computation of the geoelectric field using the method of elementary current systems and planar Earth models

Abstract. The method of spherical elementary current systems provides an accurate modelling of the horizontal component of the geomagnetic variation field. The interpolated magnetic field is used as input to calculate the horizontal geoelectric field. We use planar layered (1-D) models of the Earth's conductivity, and assume that the electric field is related to the local magnetic field by the plane wave surface impedance. There are locations in which the conductivity structure can be approximated by a 1-D model, as demonstrated with the measurements of the Baltic Electromagnetic Array Research project. To calculate geomagnetically induced currents (GIC), we need the spatially integrated electric field typically in a length scale of 100km. We show that then the spatial variation of the electric field can be neglected if we use the measured or interpolated magnetic field at the site of interest. In other words, even the simple plane wave model is fairly accurate for GIC purposes. Investigating GIC in the Finnish high-voltage power system and in the natural gas pipeline, we find a good agreement between modelled and measured values, with relative errors less than 30% for large GIC values. Key words. Geomagnetism and paleomagnetism (geomagnetic induction; rapid time variations) – Ionosphere (electric field and currents)

April 2000 geomagnetic storm: ionospheric drivers of large geomagnetically induced currents

Abstract. Geomagnetically induced currents (GIC) flowing in technological systems on the ground are a direct manifestation of space weather. Due to the proximity of very dynamic ionospheric current systems, GIC are of special interest at high latitudes, where they have been known to cause problems, for example, for normal operation of power transmission systems and buried pipelines. The basic physics underlying GIC, i.e. the magnetosphere – ionosphere interaction and electromagnetic induction in the ground, is already quite well known. However, no detailed study of the drivers of GIC has been carried out and little is known about the relative importance of different types of ionospheric current systems in terms of large GIC. In this study, the geomagnetic storm of 6–7 April 2000 is investigated. During this event, large GIC were measured in technological systems, both in Finland and in Great Britain. Therefore, this provides a basis for a detailed GIC study over a relatively large regional scale. By using GIC data and corresponding geomagnetic data from north European magnetometer networks, the ionospheric drivers of large GIC during the event were identified and analysed. Although most of the peak GIC during the storm were clearly related to substorm intensifications, there were no common characteristics discernible in substorm behaviour that could be associated with all the GIC peaks. For example, both very localized ionospheric currents structures, as well as relatively large-scale propagating structures were observed during the peaks in GIC. Only during the storm sudden commencement at the beginning of the event were large-scale GIC evident across northern Europe with coherent behaviour. The typical duration of peaks in GIC was also quite short, varying between 2–15 min.Key words. Geomagnetism and paleo-magnetism (geomagnetic induction) – Ionosphere (ionospheric disturbances) – Magnetospheric physics (storms and substorms)

Studies of space weather effects on the finnish natural gas pipeline and on the finnish high-voltage power system

Geomagnetically induced currents (GIC) in technological systems are the ground end of the complicated space weather chain. GIC are a possible source of problems to the systems. In power networks, GIC cause saturation of transformers, which may even result in a collapse of the whole system and in damage of transformers. Pipelines can suffer from problems associated with corrosion and its control. The Finnish high-voltage power grid and the Finnish natural gas pipeline have not encountered GIC harm but due to the high-latitude location of the country and to a general interest in phenomena in the auroral region, an active research of the occurrence of GIC in these systems has been continued for about twenty years. The studies carried out have contained both GIC measurements and theoretical modelling, partly based on geomagnetic data. Estimates of expectable GIC magnitudes at different sites of the systems have been derived. However, GIC values greatly depend on the network configuration, so GIC estimates need not be valid after changes in the configuration. The electric field at the Earth's surface is the key parameter when calculating GIC in a network as it is not affected by network configuration changes. Future efforts in investigations of GIC will be focused on understanding ionospheric and magnetospheric processes responsible for large GIC events.

Why utilities respect geomagnetically induced currents

It has been well known for more than 50 years that electric utilities in northern latitudes can have geomagnetically induced currents (GICs) flowing in their transmission lines and transformer ground points, and that these are caused by geomagnetic storms. Initially, these GICs were considered harmless and very little attention was paid to them. However, in the last 40 years it was realized that large GICs can flow in power systems and become problematic and even severe enough to cause a complete system shutdown. Utilities susceptible to GIC do not expect to rely on luck that the geomagnetic storm will not affect them, or if it does, the loading conditions at the time will allow enough margin to ride through it. This is precisely why many utilities today are studying the cause, effect, and mitigation of GICs and why utilities respect GICs. This paper presents a detailed discussion on how electric utilities are affected by GICs and what can be accomplished to mitigate the harmful effects.