Space Weather and Its Potential Impacts Webinar

Solar Storms Threaten Power Grids

Solar Cycle 25 reached maximum in late 2024 yet continues delivering elevated activity well into 2026, as shown by the 18 January X-class flare that spawned an S4 radiation storm monitored by ESA and multiple strong flares reported by NASA in February. These events drive coronal mass ejections that, upon reaching Earth, disturb the geomagnetic field and induce currents in conductive ground and overhead lines.

The resulting geomagnetically induced currents flow through power transformers, causing half-cycle saturation, overheating and harmonic distortions that can trip protective relays or destroy equipment outright. The benchmark 1989 Hydro-Québec collapse left six million customers without power for nine hours; New Zealand's isolated, long-distance transmission system faces comparable exposure, with Transpower maintaining explicit protocols to sectionalise the grid during extreme storms.

Stakes are concrete: each damaged 220 kV or 400 kV transformer costs tens to hundreds of millions of dollars and can take 12-24 months to replace amid global shortages. New Zealand civil-defence estimates warn of up to six days without electricity in worst-case scenarios, affecting 15,000 medically dependent households and triggering cascading failures in water, fuel and communications. Pre-emptive shutdowns alone carry a modelled $62 billion three-day economic hit.

Non-obvious angles include New Zealand's geology—resistive ground and coastal effects amplify induced voltages—and the strategic choice between voluntary, brief outages versus uncontrolled, prolonged collapse. International early-warning systems help, yet domestic operators bear the final decision on when to pull the switch, highlighting the gap between rare-event probability and the systemic dependence of a modern island economy on continuous power.