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

Divett, Tim; Richardson, Gemma; Beggan, Ciarán; Rodger, Craig J.; Boteler, D. H.; Ingham, M.; Manus, Daniel H. Mac; Thomson, Alan; Dalzell, Michael D

doi:10.1029/2018sw001814

Cited by 44 publications

(119 citation statements)

References 26 publications

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“…However, there is evidence that GMD may produce significant GIC further equatorwards, where no DC monitors are located. For example the GIC modeling reported by Divett et al (2018) showed that significant GIC is expected to occur at the top of the South Island.…”

Section: Experimental Data Setsmentioning

confidence: 99%

Geomagnetically Induced Currents and Harmonic Distortion: Storm‐Time Observations From New Zealand

et al. 2020

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Large geomagnetic storms are a known space weather hazard to power transmission networks due to the effects of geomagnetically induced currents (GICs). However, research in this area has been hampered by a lack of GIC observations. Previous studies have noted that New Zealand is unusually fortunate in having a comparatively dense, high quality, set of GIC measurements, spanning >60 transformers in >20 substations. However, due to operational reasons these observations are clustered in the mid and lower South Island. In this paper we analyze space weather‐induced GIC impact patterns over the entire country by using a different set of sensors that monitor levels of harmonic distortion, with even and odd harmonics measured separately. GICs lead to half cycle transformer saturation and is one of the few ways in which even harmonics are produced in a well‐run power transmission network. We make use of harmonic distortion measurements at 377 circuit breakers made at 126 separate locations. Focusing on the intense geomagnetic storm activity during 6–9 September 2017, we show how the even harmonic distortion observations provide a useful new picture of GIC‐stressed transformers. These observations demonstrate how GIC effects can be monitored by using even harmonic distortion in locations where no GIC measurements are present (e.g., the most of the North Island). We understand that harmonic distortion measurements are fairly common in electrical networks and could provide a new tool for space weather researchers.

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Section: Experimental Data Setsmentioning

confidence: 99%

Geomagnetically Induced Currents and Harmonic Distortion: Storm‐Time Observations From New Zealand

et al. 2020

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“…This force arises from variations in the magnetic field cutting a loop consisting of the line itself, the grounding points of the line, and a depth in the earth related to the skin depth for the magnetic field variation. Modeling of the induced electric fields and their impact on a specific transmission line topology allows prediction of the severity of the risk presented by GIC to electrical substations, or even individual transformers, in the network (see, for example, Divett et al, ).…”

Section: Introductionmentioning

confidence: 99%

Telluric Field Variations as Drivers of Variations in Cathodic Protection Potential on a Natural Gas Pipeline in New Zealand

Ingham

Rodger

2018

Space Weather

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A study of variations in cathodic protection potential on a natural gas pipeline in the North Island of New Zealand is reported. Both the measured pipe‐to‐soil potential (PSP) and the current measured through an installed defect in the pipeline coating show strong correlations with variations in measured magnetic and telluric fields. Contrary to predictions from distributed‐source transmission line theory, analysis shows that the closest correlations of PSP and current are with the component of telluric field perpendicular to the pipeline. This orientation is close to perpendicular to major electrical conductivity contrasts associated with both the local coastline and with on‐shore Earth conductivity structure. It is therefore inferred the variations in PSP which drive the variations in defect current are the result of changes in the local Earth potential. While reporting on specific observations from New Zealand, these results should be applicable across a wide range of middle and high‐latitude global locations. Estimates of possible corrosion rates for the pipeline in question suggest that such enhancement of telluric field variations by conductivity structure may pose significant risk to pipelines in the event of defects in the pipeline coating.

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“…Striking features of the calculated GIC distribution (Divett et al 2017 their Figure 8) included the high spatial variability in the GIC magnitude, and the small number of affected substations, quite in a similar manner to those observed in the UK (Beggan et al 2013 their Figure 8). A related analysis by Divett et al (2018) expanded this effort to consider transformer-level (rather than substation-level) GICs, thus eliminating one more uncertainty in the interpretation of real, transformer-level GIC measurements.…”

Section: New Zealandmentioning

confidence: 99%

The Role of Global/Regional Earth Conductivity Models in Natural Geomagnetic Hazard Mitigation

Kelbert

2019

Surv Geophys

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Geomagnetic disturbances cause perturbations in the Earth's magnetic field which, by the principle of electromagnetic induction, in turn cause electric currents to flow in the Earth. These geomagnetically induced currents (GICs) also enter man-made technological conductors that are grounded; notably, telegraph systems, submarine cables and pipelines, and, perhaps most significantly, electric power grids, where transformer groundings at power grid substations serve as entry points for GICs. The strength of the GICs that flow through a transformer depends on multiple factors, including the spatiotemporal signature of the geomagnetic disturbance, the geometry and specifications of the power grid, and the electrical conductivity structure of the Earth's subsurface. Strong GICs are hazardous to power grids and other infrastructure; for example, they can severely damage transformers and thereby cause extensive blackouts. Extreme space weather is therefore hazardous to man-made technologies. The phenomena of extreme geomagnetic disturbances, including storms and substorms, and their effects on human activity are commonly referred to as geomagnetic hazards. Here, we provide a review of relevant GIC studies from around the world and describe their common and unique features, while focusing especially on the effects that the Earth's electrical conductivity has on the GICs flowing in the electric power grids.

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

Cited by 44 publications

References 26 publications

Geomagnetically Induced Currents and Harmonic Distortion: Storm‐Time Observations From New Zealand

Geomagnetically Induced Currents and Harmonic Distortion: Storm‐Time Observations From New Zealand

Telluric Field Variations as Drivers of Variations in Cathodic Protection Potential on a Natural Gas Pipeline in New Zealand

The Role of Global/Regional Earth Conductivity Models in Natural Geomagnetic Hazard Mitigation

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