Prediction of extreme geomagnetically induced currents in the UK high‐voltage network

Abstract

[1] Geomagnetically Induced Currents (GIC) can be damaging to high-voltage power transmission systems. GIC are driven by rapid changes in the strength of the magnetic field external to the Earth's surface. Electric fields are produced in the ground by the interaction between this changing magnetic field, the sea and the conductivity structure of the Earth. Using a technique known as the "thin-sheet approximation," we can determine the electric field at the Earth's surface, which in turn allows the calculation of GIC in the earthing connections of high-voltage transformers within a power grid. We describe two new developments in the modeling of GIC in the UK, though the results are applicable to GIC-related research in other regions. Firstly, we have created an updated model of the UK surface conductivity by combining a spatial database of the UK geological properties (i.e., rock type) with an estimate of the conductivity for specific formations. Secondly, we have developed and implemented a sophisticated and up-to-date model for the 400 kV and 275 kV electrical networks across the whole of Great Britain and, in addition, the 132 kV network in Scotland. We can thus deduce the expected GIC at each transformer node in the system based on the network topology from an input surface electric field. We apply these developments to study the theoretical response of the UK high-voltage power grid to modeled extreme 100 year and 200 year space weather scenarios and to a scaled version of the

Sensitivity of geomagnetically induced currents to varying auroral electrojet and conductivity models

“…Beggan et al 2013), by scaling the electrojet H 0 to 250, 320 and 450 nT for a period (T) of 2 min and 1,250, 1,575 and 2,275 nT for a period (T) of 10 min, giving six different magnetic field strength models. The values are chosen from the work of Thomson et al (2011) based on records from European observatories over the past 30 years.…”

“…This is a modified version of the 2012 model of the UK network (Beggan et al 2013), consisting of 695 nodes and 1,178 connections. Figure 2 shows an overview of the National Grid UK high-voltage 400-and 275-kV line distribution power network model.…”

“…In contrast, nodes K and L along the south coast are less sensitive to either 1D or 2D conductivity differences. Beggan et al (2013) used the homogeneous half-space for their GIC analysis, and this has proven to be the most extreme form of 1D conductivity model. Figure 3 shows that the most important surface variations occur on the boundaries of the conductivity contrasts, i.e.…”

“…In order to increase the complexity of the geophysical and engineering layers, Beggan et al (2013) investigated the use of a more sophisticated high-voltage electrical network model coupled to a more representative two dimensional surface conductance model, as developed by Beamish and White (2012). These improvements were applied to a set of reasonable 'worst-case' magnetic field change scenarios for the UK mainland, based on work from Thomson et al (2011).…”

Influence of spatial variations of the geoelectric field on geomagnetically induced currents

“…The geoelectric field varies rapidly temporarily and spatially as demonstrated, for example, by Beggan et al (2013), Bedrosian and Love (2015), Wei et al (2013) and Wang et al (2016) for regional and continental scales, and by Püthe and Kuvshinov (2013) and Ngwira et al (2015) for global scales. Temporal variations are due to time variations of space currents and are connected with time variations of the geomagnetic field by Faraday's law.…”