GP014-0004
Geomagnetically Induced Currents in the Portuguese power network

Wednesday, 16 December 2020
Poster
Joana Ribeiro1, Pedro Baltazar-Soares2, Fernando J.G. Pinheiro1, Rute Santos3, Fernando M Santos2, Maria Alexandra Pais1 and João Cardoso4, (1)University of Coimbra, CITEUC, Department of Physics, Coimbra, Portugal, (2)Instituto Dom Luiz (IDL), Faculdade de Ciências, Universidade de Lisboa, Lisbon, Portugal, (3)University of Coimbra, Department of Physics, Coimbra, Portugal, (4)Universidade de Coimbra, LIBPhys-UC, Department of Physics, Coimbra, Portugal
Abstract:
The MAG-GIC project aims to assess the hazard associated with Geomagnetically Induced Currents (GICs) in high-voltage power lines of Portugal mainland.

GICs are a result of variations in the ionospheric and magnetospheric electric currents, that cause changes in the Earth's magnetic field. Along grounded conductive structures, the induced electric field drives electric currents in closed circuits. Extreme GICs represent a threat for man-made infrastructures such as power grids, pipelines, telecommunication cables, and railway systems. GIC hazard mitigation is important for planning and designing more resilient transmission systems.

For the characterization of the different driving sources of GICs (i.e., geomagnetic storms) we use the database of one of the oldest observatories in operation in the world, the Coimbra magnetic observatory (COI), which has been measuring (almost) continuously the geomagnetic field variations since 1866. The response to geomagnetic storms felt at the Earth surface, in terms of intensity and orientation of induced electric fields, depends strongly on the distribution of buried conductive minerals, laterally and in depth. The determination of the electrical conductivity model used in this study is obtained from the new 40 broadband MT soundings in a 50x50 km grid that covers all the territory. The study also benefits from a straight collaboration with the Portuguese high voltage power network company (REN) that gave access to realistic values for the circuit parameters.

In this work, we intend to make use of some of the available tools that have been developed by several groups working in this field and obtain a GIC estimation in the national power network for some of the strongest events during the solar cycle 24. One novelty in this study is a new 3D resistivity model, computed from MT soundings. As in general more elaborate resistivity models are not available, we analyze the influence on GICs of using simplified vs realistic conductivity models. Another novelty is the presence of shield wires in the power network model. We test the effect on GICs of these conductive lines, that add to the circuit further paths but also further driving potentials for the electric current flow.

Acknowledgments:

PTDC/CTA -GEO/31744/2017

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