ALBERT

Description: Critical infrastructures on which society depends are affected by what are known as geomagnetically induced currents. As a consequence of Faraday's law of induction, which is associated with time variations of the magnetic field, an electromotive force is induced in the conductive earth. The (geo)electric field generated in this way acts as a voltage source through the power transmission networks, so that the induced currents during large geomagnetic storms can damage the transformers where the circuit is grounded. Many countries, such as Spain, have undertaken studies aimed at assessing the vulnerability of their power grids to the danger posed by this phenomenon, but one question that remained open was whether the grids that transmit power across their islands deserve attention. We have constructed models for the grids in each of the individual systems and used resistivity models of the lithosphere for each group of islands, from which we have calculated the surface impedances. The respective models of electrical admittances of the grids have been combined with the geoelectric field derived from the convolution of the recorded (or expected in an extreme scenario) geomagnetic storms and the impedances calculated from the geoelectrical models to derive the expected GICs in the power lines, substations, and transformers. The results of our study show that the vulnerability of the Canary Islands is very low, while that of the Balearic Islands is not negligible.