Modeling Geomagnetically Induced Currents From Magnetometer Measurements: Spatial Scale Assessed With Reference Measurements

Butala, Mark D.; Kazerooni, Maryam; Makela, J. J.; Kamalabadi, F.; Gannon, J. L.; Zhu, Hao; Overbye, Thomas J.

doi:10.1002/2017sw001602

Cited by 30 publications

(22 citation statements)

References 56 publications

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“…These observations suggest that event 4 just after 12 UT on 8 September 2017 has localized magnetic field fluctuations closer to Dunedin than Eyrewell, which is consistent with the proximity of the auroral electrojet to Dunedin as identified in Figure . This is also consistent with the power grid modeling of Butala et al (), who found that the fidelity between measured GIC levels and modeling using magnetometer proxies is a function of the distance between the two measurements, with shorter separation distances providing more successful modeling outcomes. However, Middlemarch shows a similar peak H′ to EYR (29 nT/min cf.…”

Section: Magnetic Field and Gic Perturbationssupporting

confidence: 88%

Long‐Lasting Geomagnetically Induced Currents and Harmonic Distortion Observed in New Zealand During the 7–8 September 2017 Disturbed Period

et al. 2018

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Several periods of geomagnetically induced currents (GICs) were detected in the Halfway Bush substation in Dunedin, South Island, New Zealand, as a result of intense geomagnetic storm activity during 6 to 9 September 2017. Unprecedented data coverage from a unique combination of instrumentation is analyzed, that is, measurements of GIC on the single‐phase bank transformer T4 located within the substation, nearby magnetic field perturbation measurements, very low frequency (VLF) wideband measurements detecting the presence of power system harmonics, and high‐voltage harmonic distortion measurements. Two solar wind shocks occurred within 25 hr, generating four distinct periods of GIC. Two of the GIC events were associated with the arrival of the shocks themselves. These generated large but short‐lived GIC effects that resulted in no observable harmonic generation. Nearby and more distant magnetometers showed good agreement in measuring these global‐scale magnetic field perturbations. However, two subsequent longer‐lasting GIC periods, up to 30 min in duration, generated harmonics detected by the VLF receiver systems, when GIC levels continuously exceeded 15 A in T4. Nearby and more distant magnetometers showed differences in their measurements of the magnetic field perturbations at these times, suggesting the influence of small‐scale ionospheric current structures close to Dunedin. VLF receiver systems picked up harmonics from the substation, up to the 30th harmonic, consistent with observed high‐voltage increases in even harmonic distortion, along with small decreases in odd harmonic distortion.

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Section: Magnetic Field and Gic Perturbationssupporting

confidence: 88%

Long‐Lasting Geomagnetically Induced Currents and Harmonic Distortion Observed in New Zealand During the 7–8 September 2017 Disturbed Period

et al. 2018

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“…Overbye et al (2012) point out that the modeling of GIC will be greatly enhanced by comparison with observations. Butala et al (2017) provided comparison of observed and modeled transformer-level GIC using PowerWorld in the same network, also with a uniform electric field. In a further example, Shetye and Overbye (2015) modeled GIC in the same network using a single resistance for each substation.…”

Section: 1029/2018sw001814mentioning

confidence: 99%

Transformer‐Level Modeling of Geomagnetically Induced Currents in New Zealand's South Island

et al. 2018

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During space weather events, geomagnetically induced currents (GICs) can be induced in high‐voltage transmission networks, damaging individual transformers within substations. A common approach to modeling a transmission network has been to assume that every substation can be represented by a single resistance to Earth. We have extended that model by building a transformer‐level network representation of New Zealand's South Island transmission network. We represent every transformer winding at each earthed substation in the network by its known direct current resistance. Using this network representation significantly changes the GIC hazard assessment, compared to assessments based on the earlier assumption. Further, we have calculated the GIC flowing through a single phase of every individual transformer winding in the network. These transformer‐level GIC calculations show variation in GICs between transformers within a substation due to transformer characteristics and connections. The transformer‐level GIC calculations alter the hazard assessment by up to an order of magnitude in some places. In most cases the calculated GIC variations match measured variations in GIC flowing through the same transformers. This comparison with an extensive set of observations demonstrates the importance of transformer‐level GIC calculations in models used for hazard assessment.

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“…Investigations and improvements to conductivity models have been made by many, for example, Bedrosian and Love (2015), Schultz et al (2006) and Kelbert et al (2011). In a critical step to understand sources of uncertainty and error, comparisons of modeled GIC to neutral current measurements are beginning to be made (Butala et al, 2017;Kazerooni et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

A Comparison of Peak Electric Fields and GICs in the Pacific Northwest Using 1‐D and 3‐D Conductivity

et al. 2017

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Geomagnetically induced currents (GICs) are a result of the changing magnetic fields during a geomagnetic disturbance interacting with the deep conductivity structures of the Earth. When assessing GIC hazard, it is a common practice to use layer‐cake or one‐dimensional conductivity models to approximate deep Earth conductivity. In this paper, we calculate the electric field and estimate GICs induced in the long lines of a realistic system model of the Pacific Northwest, using the traditional 1‐D models, as well as 3‐D models represented by Earthscope's Electromagnetic transfer functions. The results show that the peak electric field during a given event has considerable variation across the analysis region in the Pacific Northwest, but the 1‐D physiographic approximations may accurately represent the average response of an area, although corrections are needed. Rotations caused by real deep Earth conductivity structures greatly affect the direction of the induced electric field. This effect may be just as, or more, important than peak intensity when estimating GICs induced in long bulk power system lines.

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Modeling Geomagnetically Induced Currents From Magnetometer Measurements: Spatial Scale Assessed With Reference Measurements

Cited by 30 publications

References 56 publications

Long‐Lasting Geomagnetically Induced Currents and Harmonic Distortion Observed in New Zealand During the 7–8 September 2017 Disturbed Period

Long‐Lasting Geomagnetically Induced Currents and Harmonic Distortion Observed in New Zealand During the 7–8 September 2017 Disturbed Period

Transformer‐Level Modeling of Geomagnetically Induced Currents in New Zealand's South Island

A Comparison of Peak Electric Fields and GICs in the Pacific Northwest Using 1‐D and 3‐D Conductivity

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