When the Sun unleashes its powerful storms, some of the most vulnerable pieces of human infrastructure are power grids. The mass of plasma hitting Earth’s magnetic field causes surges of current through the ground that can knock out transformers and cause entire networks to fail. This exact scenario occurred during a powerful solar storm that hit in March 1989, which caused a blackout spanning the entire Canadian province of Quebec.
In the past, power companies largely assumed that even in the strongest storms, the effects would be limited to high-latitude regions like Canada, the northern United States, and Scandinavia.
But then the “Halloween” solar storm of October 2003 struck, which damaged 12 power transformers in midlatitude South Africa, forcing them to be replaced. Since then, scientists have begun surveying and modeling power grids in midlatitude countries like Spain to determine their vulnerability to space weather.
Now Marshall et al. have performed an analysis on the power grid of eastern Australia, in Queensland and Tasmania. They combined mathematical models of space weather with maps of the power grid provided by the power companies to simulate how geomagnetic storms would affect the grid. They started by testing the model on two storms considered intense: in October 2013 and June 2015. They found that the currents of the models were very close to the actual currents that the storms induced in the power grid, which were recorded by monitoring equipment installed in 2011.
Having validated the model, they then unleashed it by feeding it space weather data from the 2003 Halloween superstorm, from before the monitoring equipment had been installed.
They found that the network in Tasmania did not experience very strong currents, partly as a result of the relatively small physical extent of the island’s power network. Induced currents were usually less than 5 amps in intense storms, with occasional spikes above 10 amps in superstorms.
However, the Queensland power network was slightly more vulnerable because its network is bigger and its power lines tend to have a dominant alignment following the continent’s northeastern coast. When the Earth’s geoelectric field happens to be oriented parallel to the coast, the induced currents tend to increase.
During intense storms, Queensland’s geoinduced currents tended to remain below 20 amps. But during superstorms, they could reach higher than 40 amps. Under such circumstances, power companies should consider precautionary action to avoid transformer damage and potential blackouts, the authors say, including reviewing planned maintenance and operating the grid to better manage the extra currents. (Space Weather, https://doi.org/10.1002/2017SW001613, 2017)
—Mark Zastrow, Freelance Writer