Geomagnetically Induced Currents in the Irish Power Network during Geomagnetic Storms

TL;DR

This study models geomagnetically induced currents in the Irish power network during major geomagnetic storms, highlighting potential risks to transformers and the importance of ground resistivity in GIC prediction.

Contribution

It introduces a simulation approach combining plane wave electric field modeling with ground resistivity data to assess GICs in Ireland during geomagnetic storms.

Findings

Peak GICs up to 23 A during large storms.

Three substations identified as high-risk locations.

Ground resistivity significantly affects GIC estimates.

Abstract

Geomagnetically induced currents (GICs) are a well-known terrestrial space weather hazard. They occur in power transmission networks and are known to have adverse effects in both high and mid-latitude countries. Here, we study GICs in the Irish power transmission network (geomagnetic latitude 54.7--58.5$^{\circ}$ N) during five geomagnetic storms (06-07 March 2016, 20-21 December 2015, 17-18 March 2015, 29-31 October 2003 and 13-14 March 1989). We simulate electric fields using a plane wave method together with two ground resistivity models, one of which is derived from magnetotelluric measurements (MT model). We then calculate GICs in the 220, 275 and 400~kV transmission network. During the largest of the storm periods studied, the peak electric field was calculated to be as large as 3.8~V~km\textsuperscript{-1}, with associated GICs of up to 23~A using our MT model. Using our homogenous resistivity model, those peak values were 1.46~V~km\textsuperscript{-1} and 25.8~A. We find that three 400 and 275~kV substations are the most likely locations for the Irish transformers to experience large GICs.