Modeling Geomagnetically Induced Currents in Australian Power Networks Using Different Conductivity Models

Abstract

Space weather manifests in power networks as quasi‐DC currents flowing in and out of the power system through the grounded neutrals of high‐voltage transformers, referred to as geomagnetically induced currents. This paper presents a comparison of modeled geomagnetically induced currents, determined using geoelectric fields derived from four different impedance models employing different conductivity structures, with geomagnetically induced current measurements from within the power system of the eastern states of Australia. The four different impedance models are a uniform conductivity model (UC), one‐dimensional n‐layered conductivity models (NU and NW), and a three‐dimensional conductivity model of the Australian region (3DM) from which magnetotelluric impedance tensors are calculated. The modeled 3DM tensors show good agreement with measured magnetotelluric tensors obtained from recently released data from the Australian Lithospheric Architecture Magnetotelluric Project. The four different impedance models are applied to a network model for four geomagnetic storms of solar cycle 24 and compared with observations from up to eight different locations within the network. The models are assessed using several statistical performance parameters. For correlation values greater than 0.8 and amplitude scale factors less than 2, the 3DM model performs better than the simpler conductivity models. When considering the model performance parameter, P, the highest individual P value was for the 3DM model. The implications of the results are discussed in terms of the underlying geological structures and the power network electrical parameters.

Intensity and Impact of the New York Railroad Superstorm of May 1921

“…Recent integrations have brought this theory into quantitative focus. Three separate factors are important (e.g., Blake et al, ; Lucas et al, ; Mac Manus et al, ; Marshall et al, ; Torta et al, ): (1) the localized details of geomagnetic vector disturbance responsible for the induction in the Earth, (2) the geographic expression of the Earth's surface impedance tensor, giving the frequency dependent relationship between the inducing geomagnetic disturbance and the induced geoelectric field, and (3) the topology of the conducting network, since geomagnetically induced voltage is determined by the integrated projection of the geoelectric field onto line segments connecting grounding points. A conspiracy of these factors together allowed the magnetic storm of May 1921 to adversely impact the telephone and telegraph networks of New York, some of which were either colocated with or used to support the operation of train systems.…”

Exploring the Influence of Lateral Conductivity Contrasts on the Storm Time Behavior of the Ground Electric Field in the Eastern United States

“…Computations of the GEF within the second, most populated, group of papers (Beggan et al, ; Bailey et al, , ; Divett et al, ; Dimmock et al, ; Liu et al, ; Marshall et al, ; Nakamura et al, ; Püthe & Kuvshinov, ; Püthe et al, ; Pokhrel et al, ; Rosenqvist & Hall, ; Wang et al, , among others) rely on a numerical modeling of the GEF, either with a thin sheet or fully 3‐D conductivity models of the Earth. 3‐D conductivity models can be compiled using, for instance, results of regional MT surveys or/and exploiting global and regional maps of bathymetry, sediment thickness, etc.…”

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

“…These developments have enabled derivation of fully 3D electrical conductivity models that are now becoming available for geomagnetic hazard applications. In fact, while the plane-wave Starting with the empirical geomagnetic and magnetotelluric data (green), one could either use interpolation methods to estimate real-time gridded geoelectric fields ("data-space workflow," shown in blue; e.g., Bonner and Schultz 2017;Campanyà et al 2019), or a conductivity model could be used for a physics-based variant of the interpolation ("model-space workflow," shown in red, e.g., Marshall et al 2019). Method 1: interpolation using multi-station transfer functions; not based on physics.…”

“…Indeed, a state-of-the-art validation analysis of GIC modeling using multiple different conductivity model formulations in Australia was recently published by Marshall et al (2019). Four electrical conductivity models were set up with varying degrees of complexity, ranging from a uniform conductivity model, to a couple of 1D models, to a fully 3D model, derived from AWAGS magnetometer data as in Wang et al (2014), from which gridded impedance data were then produced (as described in Fig.…”

“…Overall, the 3D model was found to perform better than the simpler conductivity models, but with some caveats. According to Marshall et al (2019), the relatively good performance of all models could be attributed to the reduced coast effect and otherwise relatively high conductivity of the Earth beneath the footprint of this power grid. The 3D conductivity model resolution could also be substantially improved by applying community MT inversion software (e.g., Kelbert et al 2014) to the newly obtained AusLAMP MT data; this higher-resolution model could then be combined with the coarser AWAGSderived model at depths.…”