On extreme GIC values affecting the Portuguese power grid 

Fernando Pinheiro - University of Coimbra, Portugal; Joana Alves Ribeiro - University of Coimbra and University of Lisbon, Portugal; Anna Morozova - University of Coimbra, Portugal; Fernando Monteiro Santos - University of Lisbon, Portugal; Pedro Baltazar-Soares - University of Lisbon, Portugal; Paulo Ribeiro - University of Coimbra, Portugal; João Fernandes - University of Coimbra, Portugal; Maria Alexandra Pais - University of Coimbra, Portugal

Session: Ground-Level Geomagnetically Induced Currents

Abstract

A magnetic superstorm occurred in October/November 1903, close to the minimum of solar cycle 14, and is well documented by variograms from Coimbra magnetic observatory (COI). During this storm, the alternative index Dst’ attained an extreme value -513 nT (Hayakawa et al., 2020). If such a storm occurred today, how large could be the currents induced along the grounded conductors of the Portuguese power system network?
In this presentation, we assess the repercussions that a geomagnetic storm similar to the one on the 31st October 1903 (one of the largest events registered at COI) would have in the current southern Portuguese power system network. In order to achieve this goal, we i) build a power transmission grid model taking into account information provided by the national power network operator, REN; ii) analyse COI station's magnetograms for the 1903 storm and other historical events, as well as 1-min series from some of the strongest events of solar cycle 24; iii) compare the state of geomagnetic activity with the solar surface state for the strongest events; iv) evaluate the impact of different ground resistivity models, including the results from MT soundings, on GICs and on the geoelectric fields that drive them.