In this work, we describe an approach to characterize the ground response to geomagnetic storm drivers and recalculate the scaling factors that are used in the North American Reliability Corporation (NERC) TPL-007 geomagnetic disturbance (GMD) standard based on magnetotelluric (MT) survey measurements. The new ground response scaling factors indicate a significantly wider range of ground responses from the one-dimensional model responses used in the original NERC GMD standards framework. Further, the region Mid-West area west of the great lakes and North-East around New England and areas along the Appalachian Mountains appear to be particularly exposed to the geoelectric field hazard under extreme space weather conditions. A more complete validation of MT data in geomagnetically induced currents applications is warranted before usage of the presented results as a basis for possible updates to the NERC GMD standard.

The analysis of Geomagnetically Induced Current (GIC) flows at a system scale is a relatively mature feature of bulk power system planning tools. The study of GIC-related harmonics mitigation strategies at the system scale is still a gap in the industry. EPRI developed the publicly available GIC-related harmonic analysis tool (GICharm) with the objective of addressing this gap. As a continuation of the efforts to increase industry confidence in GICharm, this paper compares its accuracy against time domain simulations using the commercial software tool EMTP. The paper utilizes the well-known Western System Coordinating Council (WSCC) 9-bus system under a Geomagnetic Disturbance (GMD) scenario. Frequency scans, voltage and current waveforms, and Voltage Total Harmonic Distortion (VTHD) are obtained from both tools and compared to provide a high level of detail. A brief computational-time comparison discussion is also included. The paper also discusses all the necessary modeling details for each component in the test system, starting from publicly available positive-sequence information. It also describes the assumptions made to define a multi phase model from the positive-sequence information, as well as the steps taken to create both GICharm and EMTP models.

The impact of geomagnetic disturbances (GMDs) continues to be a significant concern for the North American bulk power system (BPS). In order to assess potential system vulnerabilities and evaluate appropriate mitigation measures, several planning studies must be performed in conjunction, as outlined in the NERC Reliability GMD Vulnerability Assessment Requirement (TPL-007). Presently these studies are conducted across multiple software platforms which requires multiple databases and user intervention. This paper presents a tool that integrates the TPL-007 studies across these multiple platforms, enhancing the accuracy and efficiency of the GMD vulnerability assessment.

The increasing penetration of inverter-based resources at the distribution and transmission levels, the proliferation of weaker, microgrid-based systems as well as geomagnetic disturbances impact have raised concerns related to increasing harmonic distortion in electric power systems. While not a new issue, systematic and robust simulation-based approaches are required to analyze harmonics impacts more than ever. This paper compares the accuracy of the new harmonics modeling and simulation capability in a familiar commercial power systems analysis tool (Siemens's PSS (R) E) with an open-source tool (EPRI's OpenDSS). Both are widely used in academia and in the industry. Frequency scans and Voltage Total Harmonic Distortion (VTHD) and Current Total Harmonic Distortion (CTHD) are computed in both tools and benchmarked against test system results published by IEEE Harmonics Modeling and Simulation Task Force. The paper also presents the modeling details for each component in the test system and shows that both tools produce similar results. It also describes inaccuracies that were discovered in the published test system's VTHD results for two locations within the benchmark system.

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.

Our current knowledge of the geomagnetic poleward and equatorward boundary dynamics is limited, particularly, how deep those two latitudinal boundaries can extend into lower geomagnetic latitudes during magnetic storms. We want to understand the motion of the boundary because it is important in terms of the location and magnitude of the effects of geomagnetic disturbances associated with storms on the ground. In this study we derive spherical elementary ionospheric currents from ground magnetometer arrays covering North America and Greenland during six magnetic storms in 2015 and 2018. With two dimensional maps of the auroral region current, we select the equatorward boundary of the region 2 currents by‐eye and fit the boundary with an ellipse to derive the location of the equatorward boundary at magnetic midnight. We have obtained over 500 boundaries and find that the midnight boundary location varies between 45° and 66° magnetic latitude. We examine the influence of the interplanetary magnetic field (IMF), solar wind plasma, and geomagnetic indices on the location of the magnetic midnight equatorial boundary and find that the equatorial boundary location is best correlated with the IMF Bz, VBz, and the Sym‐H index. We demonstrate that as the Bz component becomes more negative, the magnitude of VBz increases, and the magnitude of the Sym‐H index increases, the magnetic midnight equatorial boundary shifts equatorward during periods of moderate to high geomagnetic activity.

The part-cycle saturation of power transformers caused by the flow of Geomagnetically-Induced Currents (GIC) through power transformers is the root cause of the GIC issues which impact the bulk power system. One of the modeling assumptions made in Geomagnetic Disturbance (GMD) vulnerability assessments is that GIC is purely a common-mode signal. That is, it flows equally in all three phases of the power system, combining and returning through the neutral connection of a grid-connected wye transformers. This paper describes the impact of unbalanced GIC on grid-connected transformers. Field measurements were investigated to determine a realistic value of GIC current unbalance. The last section of this paper briefly discusses conclusions of the study and next steps.

During geomagnetic disturbance (GMD) events, variations in the Earth's magnetic field induce low-frequency currents (relative to power system frequencies) in the power grid.These lowfrequency currents are referred to as geomagnetically-induced current or GIC.The impacts of GIC on the power grid can range from thermal damage to bulk power transformers to voltage collapse.On March 13, 1989, the Hydro Quebec system experienced a blackout resulting from a severe GMD event.

An expanded budget is needed for the newly-formed NASA Heliophysics Space Weather Program, at a level of $100-200M per

<p>Human technology is vulnerable to space weather, a natural hazard. High-voltage electric power transmission grids constitute one of the most critical man-made technological systems vulnerable to space weather driven geomagnetically induced currents (GICs). In this study, we perform an analysis of (1) measured GIC data collected at mid-latitudes by U.S. power utilities during the period from 2010 to 2021, and (2) the corresponding geomagnetic field information for each event. The study includes a statistical analysis of all events and an overview of the top three highest GIC recordings in the data. We show that roughly 80% of the events are associated with the main phase of geomagnetic storms, while about 20% are associated with sudden storm commencement.</p>

This report documents the specification and validation of a harmonic modeling approach and model for inverter-based resources like solar photovoltaic (PV) inverters in both the frequency domain and the electro-magnetic transients (EMT) time domain.

This research project will address the most pressing uncertainties in modeling and measuring the electric power grid effects of geomagnetic disturbances (GMDs) and the E3 portion of nuclear electromagnetic pulse (EMP). The primary goal is to help decision-makers in the electric power sector have the knowledge and tools they need to most effectively mitigate GMD effects on our nation's electric grid, with a secondary focus on EMP. Comprehensive modeling, model assessment through sensitivity analysis, and validation with field measurement data will be the primary tasks undertaken. The goal will be a more widespread adoption of these modeling approaches, namely characterizing the uncertainty associated with these models and how that uncertainty will affect decision-making by industry. This document summarizes industry requirements for better decision-making tools, informed by feedback from an industry advisory board. These requirements help guide planning and execution of the project's remaining tasks.

Abstract Geomagnetically induced currents (GICs) at middle latitudes have received increased attention after reported power grid disruptions due to geomagnetic disturbances. However, quantifying the risk to the electric power grid at middle latitudes is difficult without understanding how the GIC sensors respond to geomagnetic activity on a daily basis. Therefore, in this study the question “Do measured GICs have distinguishable and quantifiable long‐period and short‐period characteristics?” is addressed. The study focuses on the long‐term variability of measured GIC, and establishes the extent to which the variability relates to quiet‐time geomagnetic activity. GIC quiet‐day curves (QDCs) are computed from measured data for each GIC node, covering all four seasons, and then compared with the seasonal variability of thermosphere‐ionosphere‐electrodynamics general circulation model (TIE‐GCM)‐simulated neutral wind and height‐integrated current density. The results show strong evidence that the middle‐latitude nodes routinely respond to the tidal‐driven Sq variation, with a local time and seasonal dependence on the direction of the ionospheric currents, which is specific to each node. The strong dependence of GICs on the Sq currents demonstrates that the GIC QDCs may be employed as a robust baseline from which to quantify the significance of GICs during geomagnetically active times and to isolate those variations to study independently. The QDC‐based significance score computed in this study provides power utilities with a node‐specific measure of the geomagnetic significance of a given GIC observation. Finally, this study shows that the power grid acts as a giant sensor that may detect ionospheric current systems.

Power systems can and have been impacted by harmonics generated during geomagnetic disturbances (GMD) events. These harmonics are generated from the part-cycle saturation of power transformers caused by the flow of Geomagnetically-Induced Currents (GIC) through grid-connected transformers. This paper describes a system level harmonic analysis tool needed by the industry to perform an adequate assessment of GMD-related distortion impacts. When the results of a properly performed harmonic assessment are combined with the fundamental frequency analyses, a much more accurate evaluation of grid security during GMD can be obtained. The tool is publicly available for engineers, students, and researchers. It provides multiple examples, including a validation against published measurements from an experimental setup consisting of two back-to- back connected transformers in the Fingrid power network. The last section of this paper briefly discusses the results of that validation.

Earth and Space Science Open Archive PosterOpen AccessYou are viewing the latest version by default [v1]The Heliophysics and Space Weather Open Knowledge Network: The Convergence Hub for the Exploration of Space Science (CHESS)Authors Ryan McGranaghan iD Adam Kellerman iD Robert Arritt iD Jacob Bortnik iD Morris Cohen iD Karthik Venkataramani iD Jackson McCormick Joseph Hughes iD Chigo Ngwira Charles Perry iDSee all authors Ryan McGranaghaniDCorresponding Author• Submitting AuthorASTRA LLCiDhttps://orcid.org/0000-0002-9605-0007view email addressThe email was not providedcopy email addressAdam KellermaniDUCLAiDhttps://orcid.org/0000-0002-2315-936Xview email addressThe email was not providedcopy email addressRobert ArrittiDEPRI SolutionsiDhttps://orcid.org/0000-0002-6125-0519view email addressThe email was not providedcopy email addressJacob BortnikiDUCLAiDhttps://orcid.org/0000-0001-8811-8836view email addressThe email was not providedcopy email addressMorris CoheniDGeorgia Institute of TechnologyiDhttps://orcid.org/0000-0002-7920-5759view email addressThe email was not providedcopy email addressKarthik VenkataramaniiDASTRA LLCiDhttps://orcid.org/0000-0003-2712-9210view email addressThe email was not providedcopy email addressJackson McCormickGeorgia Institute of Technologyview email addressThe email was not providedcopy email addressJoseph HughesiDASTRA LLCiDhttps://orcid.org/0000-0002-7638-2717view email addressThe email was not providedcopy email addressChigo NgwiraASTRA LLCview email addressThe email was not providedcopy email addressCharles PerryiDEPRI SolutionsiDhttps://orcid.org/0000-0001-9338-4426view email addressThe email was not providedcopy email address

Load allocations for distribution system analysis is one area in system modelling where simple, generalized assumptions are commonly made by distribution planners for lack of better data. Most of the time, the assumptions are based on measurements taken only at the distribution substation bus or at the feeder head. With widespread application of advanced metering infrastructure (AMI) technologies, loading estimates for distribution system analysis can now be based on actual measurements taken at individual loads. This can result in greatly improved accuracy in distribution power flow analysis. Three techniques for load allocation are analyzed and compared to the case with actual AMI data for all customers. Selected details of the test circuit and analysis process are provided.