Power grids face unexpected slow-burn threat from solar storms, Pg13

Key Highlights:

• A new study reveals that geomagnetic storms pose an unexpected "slow-burn" threat to interconnected power grids.
• A G4 (severe) geomagnetic storm in June 2015 caused prolonged, low-amplitude currents in New Zealand's South Island power grid.
• These sustained 20-ampere currents, though not spiking, can lead to transformer overheating and wear over time.
• The study, published in Space Weather, suggests a "mid-latitude ionospheric current wedge" as a possible cause for this phenomenon.
• Existing monitoring tools, such as the rate of change of Earth's horizontal magnetic field (H'), did not adequately capture these prolonged effects.

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Detailed Insights:

• Geomagnetic storms are temporary disturbances in Earth’s magnetic field caused by charged particles from the sun.
• The 2015 event saw geomagnetically induced currents ramp up over 90 minutes, rather than intensely spiking.
• Prolonged current flow can saturate the magnetic cores of transformers, causing them to overheat and suffer increased wear.
• Researchers from the University of Gothenburg utilized multiple datasets, including measurements from Transpower New Zealand.
• The "mid-latitude ionospheric current wedge" is believed to have diverted part of the ring current into the ionosphere.
• The risk of such unusual events is influenced by local ground conductivity and the specific layout of power lines.
• Experts need to update their understanding of space weather dangers and protective measures beyond focusing solely on current spikes.

Scientific/Technical Concepts Involved:

• Geomagnetic Storm: A temporary disturbance of the Earth's magnetosphere caused by solar wind shock waves or magnetic clouds interacting with Earth's magnetic field.
• Geomagnetically Induced Currents (GICs): Electric currents induced in long conductors like power lines due to rapid changes in Earth's magnetic field during geomagnetic storms.
• Ring Current: A toroidal current of energetic charged particles trapped in Earth's magnetic field, encircling the Earth at equatorial latitudes.
• Ionosphere: A region of Earth's upper atmosphere where atoms and molecules are ionized by solar radiation, affecting radio wave propagation.