First Estimations of Geomagnetically Induced Currents in the South of Portugal

Abstract

Geomagnetic storms induce electric fields in the conducting Earth, which are the source of geomagnetically induced currents (GICs) in grounded power lines. In this study, we compute time‐varying geoelectric fields induced in the southern region of the Portuguese mainland at the time of the strongest geomagnetic storms during solar cycle 24, using a plane‐wave approximation. The driving geomagnetic storm signals are obtained from series recorded at the Coimbra magnetic observatory. Magnetotelluric impedance tensors used to compute the induced electric field are obtained using a conductivity model that takes into account general features of the local lithology and the proximity to the sea. The first GIC simulations for Portugal are presented, using data from the national high voltage power network. Starting with an a priori standard uniform electric field to compute electromotive forces, we first assess the susceptibility of the power system network given only its topology and resistance parameters. For real storms, we report (i) the clustering of the horizontal geomagnetic time variation around the northwest‐southeast direction, (ii) the simulation of the effect of the western and southern coastlines of the territory over the induced electric field, and (iii) the spotting of the substations most sensitive to storms in the studied region.

Toward More Accurate GIC Estimations in the Portuguese Power Network

“…In this article, we present the first GIC computations for the entire Portuguese mainland high voltage power network (400, 220, and 150 kV) based on realistic local properties. Two main improvements are brought to the model, in comparison to previous work (Alves Ribeiro et al., 2021), allowing to estimate the geomagnetically induced electric fields and the related driven GICs with higher accuracy: A new 3D conductivity model (the B‐S model), inverted from 31 MT broadband soundings covering the entire national territory; Information on the circuit parameters for the full power transmission grid. …”

“…In this study, we focused on the most intense geomagnetic storms of solar cycle 24 (Table 1 and Figure 2), whose origin were coronal mass ejections (e.g., Watari, 2017). To characterize the magnitude of GICs computed for a given storm, we chose the standard deviation statistic, SD(GIC), as this represents the level of GIC activity during the whole storm duration (see also Alves Ribeiro et al., 2021): $$$\mathrm{SD}\,(GIC)=\sqrt{\frac{\sum\limits _{i}{\left(GIC\left({t}_{i}\right)-\overline{GIC}\right)}^{2}}{N-1}}$$$ with N the number of 1‐min values and $$\overline{GIC}$$ the average value in the storm time interval. This choice, instead of GIC peak values, is due to the fact that the latter can be erroneously identified from outliers and also because GIC peak values are not necessarily simultaneous over the whole power grid (Girgis et al., 2020).…”

“…Mid‐latitude power networks are also considered at risk, as can be concluded from the report of important failures that took place in South Africa (Gaunt & Coetzee, 2007) and New Zealand (Marshall et al., 2012). In the framework of project MAG‐GIC (https://www.uc.pt/en/org/maggic), the first simulations for the Portugal mainland power network (Alves Ribeiro et al., 2021) used a simplified 3D conductivity model for the southern region. That is, lateral heterogeneities in electrical conductivity were included through ocean‐land conductivity contrasts and concerned only the upper 4–5 km of crust.…”

Ensemble deep learning models for prediction and uncertainty quantification of ground magnetic perturbation

“…In addition, GICs in the power network can be simulated numerically, but this requires information on the structure and components of the power networks (e.g., transformer types, DC resistances etc.) (Boteler and Pirjola 2014;Blake et al, 2018;Alves Ribeiro et al, 2021). The literature includes studies detailing successful collaboration between power transmission operators and researchers to study GIC (Alves Ribeiro et al, 2021).…”

“…(Boteler and Pirjola 2014;Blake et al, 2018;Alves Ribeiro et al, 2021). The literature includes studies detailing successful collaboration between power transmission operators and researchers to study GIC (Alves Ribeiro et al, 2021). However, it has been noted that the information on power networks is not frequently made available to the wider scientific community by the power operators (Blake et al, 2018;Pinto et al, 2022).…”