1] Infrastructures such as pipelines and power networks at low-middle latitude regions have historically been considered relatively immune to geomagnetically induced currents (GICs). Over the past decade there have been an increasing number of investigations into the impact of GICs in long grounded conductors at these latitudes. The Australian region power network spans thousands of kilometers from low to middle latitudes. The approaching maximum of solar cycle 24 and recent findings of studies into power networks located at similar latitudes have stimulated the Australian power industry to better understand this phenomenon in their region. As a result, a pilot study to compare space weather activity with in situ GIC monitors at strategic locations within the power network was initiated. This paper provides some results from the first of these operational GIC monitors during a modest geomagnetic storm, showing the first observational evidence of space weather well correlated with GICs measured in the Australian power network. Transformer neutral currents show a high degree of similarity with the geoelectric field derived from the closest available geomagnetic observatory. Current maxima of 4-5 amperes were observed in association with geoelectric field values of 0.06-0.07 volts per kilometer. This paper also discusses the GIC measurements obtained during this storm in terms of the space weather drivers and the considerably larger geoelectric field values anticipated during larger geomagnetic storms.

Space weather manifests in power networks as quasi‐DC currents flowing in and out of the power system through the grounded neutrals of high‐voltage transformers, referred to as geomagnetically induced currents. This paper presents a comparison of modeled geomagnetically induced currents, determined using geoelectric fields derived from four different impedance models employing different conductivity structures, with geomagnetically induced current measurements from within the power system of the eastern states of Australia. The four different impedance models are a uniform conductivity model (UC), one‐dimensional n‐layered conductivity models (NU and NW), and a three‐dimensional conductivity model of the Australian region (3DM) from which magnetotelluric impedance tensors are calculated. The modeled 3DM tensors show good agreement with measured magnetotelluric tensors obtained from recently released data from the Australian Lithospheric Architecture Magnetotelluric Project. The four different impedance models are applied to a network model for four geomagnetic storms of solar cycle 24 and compared with observations from up to eight different locations within the network. The models are assessed using several statistical performance parameters. For correlation values greater than 0.8 and amplitude scale factors less than 2, the 3DM model performs better than the simpler conductivity models. When considering the model performance parameter, P, the highest individual P value was for the 3DM model. The implications of the results are discussed in terms of the underlying geological structures and the power network electrical parameters.

Geomagnetic induced currents (GICs) have been considered an issue for high‐latitude power networks for some decades. More recently, GICs have been observed and studied in power networks located in lower latitude regions. This paper presents the results of a model aimed at predicting and understanding the impact of geomagnetic storms on power networks in Australia, with particular focus on the Queensland and Tasmanian networks. The model incorporates a “geoelectric field” determined using a plane wave magnetic field incident on a uniform conducting Earth, and the network model developed by Lehtinen and Pirjola (1985). Model results for two intense geomagnetic storms of solar cycle 24 are compared with transformer neutral monitors at three locations within the Queensland network and one location within the Tasmanian network. The model is then used to assess the impacts of the superintense geomagnetic storm of 29–31 October 2003 on the flow of GICs within these networks. The model results show good correlation with the observations with coefficients ranging from 0.73 to 0.96 across the observing sites. For Queensland, modeled GIC magnitudes during the superstorm of 29–31 October 2003 exceed 40 A with the larger GICs occurring in the south‐east section of the network. Modeled GICs in Tasmania for the same storm do not exceed 30 A. The larger distance spans and general east‐west alignment of the southern section of the Queensland network, in conjunction with some relatively low branch resistance values, result in larger modeled GICs despite Queensland being a lower latitude network than Tasmania.

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