Toward More Accurate GIC Estimations in the Portuguese Power Network

Abstract

New geomagnetically induced current (GIC) computations for mainland Portugal include the entire power network, with network parameters and topology provided by the transmission grid operator for all the high voltage lines (150, 220, and 400 kV). The first 3D conductivity model for the west region of the Iberian Peninsula, based on 31 broadband magnetotelluric soundings, is used in calculations, revealing the effect of different crustal domains in GIC distribution. Geomagnetic field variations are taken from Coimbra or San Fernando magnetic observatories, according to the Nearest Neighbor method, and used together with surface impedance values predicted from the new conductivity model to calculate the induced electric field on a regular grid. The global distribution of GICs over the power network is characterized based on results derived for the eight most significant storms registered in the Iberia during solar cycle 24. Substations susceptible to the highest GICs are found near the transition between the granitic geotectonic unit of Central Iberian Zone and the Lusitanian Basin. A prototype of a Hall effect sensor has been installed at a substation and is active since the end of August 2021. In order to validate our GIC model, recent measurements are compared with simulations. GIC computation is prone to uncertainties from various sources, possibly contributing with different weights to the final error in computed values. Here, we evaluate the contribution of substation earthing resistance and nonuniqueness of the conductivity model to the final GIC uncertainties.

Mapping Geoelectric Field Hazards in Ireland

“…Most literature modeling GIC uses 1D and 2D geoelectric fields (e.g., Bailey et al, 2017;Beggan et al, 2013;Blake et al, 2018;Guo et al, 2015;Kelly et al, 2017), due to the lack of available 3D MT-TF, or 3D geoelectrical resistivity models at the time. However, with the growing availability of new 3D MT data, more research is now beginning to use 3D models (e.g., Alves Ribeiro et al, 2023;Marshall et al, 2019;Torta et al, 2017) to simulate GIC, to include the effect of directionality, which should significantly improve the accuracy of modeling. This directionality can drastically change the output GIC, as explored by Heyns et al (2021), where they measure the effects of directionality directly on GIC.…”

Modeling Geomagnetically Induced Currents in the Alberta Power Network: Comparison and Validation Using Hall Probe Measurements During a Magnetic Storm

“…For lines without resistance data, the median value of lines of the same voltage level were used (i.e., a fixed resistance of 0.042 Ω/km for 500 kV lines and 0.094 Ω/km for 240 kV lines). Note that having more than 40% of substation earthing resistance information and nearly 50% of transmission line resistance information is an improvement as compared to most previous GIC studies which often have limited network resistance information and/or assume a single earthing resistance value for all substations (e.g., Alves Ribeiro et al, 2023;Caraballo et al, 2020;Divett et al, 2020;Kelly et al, 2017;Marshall et al, 2017;Torta et al, 2014).…”

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