A preliminary risk assessment of the Australian region power network to space weather

It is well documented that power networks at high latitudes are vulnerable to the effects of space weather. In recent years the eastern Australia state power networks have been connected across state boundaries in order to improve robustness under increasing load demands and deliver power at competitive prices. However, this interconnectivity is likely to increase susceptibility of the network to space weather. Geomagnetically induced currents (GICs) flow in power transmission lines as the result of geoelectric fields and their associated geomagnetic field variations according to Faraday's Law. In this paper previously documented occurrences of GIC activity from regions around the world are investigated and categorized by their effects on nearby power networks. A frequency domain filter that produces an index representing GIC activity is applied to geomagnetic field data recorded at locations near the documented GIC activity to determine risk level GIC index thresholds. Geomagnetic field data from the Australian region are processed using the GIC filter to provide a preliminary risk assessment of space weather related GIC activity to the Australian power network. The analysis suggests lower limit threshold GIC(y) indices of 50, 100, 250, and 600 corresponding to the risk levels of low, moderate, high, and extreme, respectively. Analysis of GICy indices derived from Australian magnetometer data shows that only southern Australian regions reached the moderate risk levels defined in this study with mainland southern Australia stations reaching this risk level twice over the previous two solar cycles. Southern Australian regions such as Tasmania reached moderate levels approximately 20 times during the previous solar cycle. Furthermore, elevated risk levels are typically only observed in Australia during solar maximum and its decline phase.