A geomagnetic storm, also known as a geomagnetic disturbance (GMD), is a major disturbance of the Earth’s magnetic field caused by solar activity. A geomagnetic storm induces electric currents in the Earth that feed into power lines through substation neutral earthing, causing instabilities and even blackouts in electricity transmission systems. The strength of geomagnetically induced currents (GICs) in the ground is directly related to the electrical conductivity of the surrounding geology. GICs experienced within power transmission lines are also influenced by the orientations and configuration of the power lines with respect to the electric fields. We installed a geoelectric field monitoring system at the Canberra geomagnetic observatory (CNB) to directly measure geomagnetically induced electric fields. This data enhances the capability in modelling and forecasting geoelectric hazards and can be used to validate the modelling approach through convolving magnetotelluric (MT) tensors with geomagnetic fields. In this presentation, we modelled the induced electric fields for the 1989 Québec geomagnetic storm, using MT data collected at survey sites from the Australian Lithospheric Architecture Magnetotelluric Project (AusLAMP). These results give us insight into the potential magnitude of space weather hazards to Australia's modern-day power grids. We extended this approach to a ‘Carrington-class’ geomagnetic storm to evaluate geoelectric fields in the Australian region, allowing GICs flow in the power lines to be estimated. As an example, geomagnetically induced voltages in transmission lines from Queensland for a ‘Carrington-class’ geomagnetic storm are presented. Presented at the 2024 Australian Society of Exploration Geophysicists (ASEG) 2024 Discover Symposium

A geomagnetic storm, also known as a geomagnetic disturbance (GMD), is a major disturbance of the Earth’s magnetic field caused by solar activity. A geomagnetic storm induces electric currents in the Earth that feed into power lines through substation neutral earthing, causing instabilities and even blackouts in electricity transmission systems. The intensity of geomagnetically induced currents (GICs) is closely associated with the electrical conductivity of the surrounding geology. In this paper, we analyse one of the most well-known geomagnetic storms, the 1989 “Québec storm” and 688 magnetotelluric (MT) survey sites from the Australian Lithospheric Architecture Magnetotelluric Project (AusLAMP) to gain insight into the space weather hazard posed for Australia's modern-day power grids. Transmission lines may exhibit local maxima at differing times depending on their spatial orientation and length with respect to the time-varying magnetic field. Localised peak voltages over 100 V can be observed on some individual lines. This assessment identifies the distribution of GICs in south-eastern Australia for the 1989 Québec storm and transmission lines that are more vulnerable to GICs. It is relevant to national strategies and risk assessment procedures to mitigate space weather hazards in the Australian high-voltage power grid and the design of a more resilient power transmission system. We also analyse the 2015 “St Patrick’s Day storm” to study under-estimation of the space weather hazard associated with the band-limited geomagnetic data and MT data sets. <b>Citation:</B> Liejun Wang, Jingming Duan, Adrian P. Hitchman, Matthew G. Gard, Richard A. Marshall, Andrew M. Lewis & William V. Jones (2023) AusLAMP shines a light on space weather hazards in the Australian high-voltage power grid, <i>Exploration Geophysics</i>, DOI: 10.1080/08123985.2023.2281617