Geomagnetically Induced Currents in the Irish Power Network during Geomagnetic Storms

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.

Geomagnetically Induced Currents in the Irish Power Network During Geomagnetic Storms

The paper by Blake et al. presents a thorough examination of geomagnetically induced currents (GICs) within the Irish power network, which are particularly prevalent during geomagnetic storms. These phenomena pose significant risks to power grids, especially in mid- and high-latitude regions. The research focuses on the Irish power transmission system's response during five distinct geomagnetic storm events: March 1989, October 2003, March 2015, December 2015, and March 2016.

The study innovatively simulates electric fields using a plane wave method combined with a multi-layered resistivity model derived from magnetotelluric measurements. This resistivity model, tailored to a depth of 200 km, highlights the geological variations across Ireland. The effectiveness of using this model is compared against a homogeneous resistivity model and an existing European model (\citet{Adam2012}).

Numerical Results and Observations

Through their simulation, the authors provide precise calculations of the surface electric fields and the resultant GICs in Ireland's high-voltage network (220, 275, and 400 kV). During the most severe storm examined (March 1989), peak electric fields reached up to 3.85 V/km using the MT model, and corresponding GICs peaked at 23.1 A. Notably, during less severe storms such as those in December 2015 and March 2016, peak GICs were much lower, demonstrating the variability in GIC strength relative to geomagnetic storm intensity.

A key observation is the identification of specific substations that are likely to experience significant GICs. The study pinpointed the Moneypoint, Ballylumford, and Kilroot substations as particularly susceptible locations due to their configuration and regional geomagnetic factors.

Implications

This research has both theoretical and practical significance. The authors demonstrate the viability of using MT-derived resistivity models for estimating electric fields and GICs, showing marginal improvements over simpler homogeneous models. Real-world applications of this research are significant for power operators in Ireland and similar mid-latitude regions. They can use such models to predict and mitigate the effects of GICs during geomagnetic storms.

Future Directions

The study underscores the need for ongoing research into GICs and their effects on power grids. Enhancements in spatial resolution of conductivity models, incorporation of coastal effects into simulations, and refining the representation of power networks could lead to further improvements in the accuracy of GIC predictions. Additionally, research into statistical analyses of historical geomagnetic data could provide insights into GIC risk assessments over extended periods.

Continual monitoring, such as the placement of additional GIC probes, and collaboration between geomagnetic observatories and power companies will be crucial for further research and practical applications in GIC management. This paper sets a foundation for future studies aiming to understand and counter the impacts of geomagnetic storms on power systems globally.