13 Nov 2025
Transpower has lifted the grid emergency that was issued yesterday afternoon now that the G4 geomagnetic storm has reduced in severity.
The South Island electricity transmission lines that were removed from service as a precaution to prevent damage to equipment have now been returned to service.
There was no impact on consumers’ electricity as a result of the storm.
Transpower said the actions taken are part of its response plan to space weather when it reaches a particular level and has been developed over several years through work with Otago University, international space agencies and others in the electricity industry.
Although New Zealand is well prepared for geomagnetic storms, Transpower said it is a timely reminder to Kiwis that they should be prepared for a natural disaster or other major event that could interrupt their power supply and damage other infrastructure.
Background
Transpower not only monitors weather here in Aotearoa but also weather in space that can affect our power system.
Space weather is when the Sun ejects plasma and other matter in Earth’s direction. These coronal mass ejections (CME) are rare, and most people won’t notice because our planet’s magnetic field shields us from the particles.
However, these CMEs can cause geomagnetic storms on Earth, and these storms can send unwanted currents through the long electricity circuits that we manage. When the currents reach transformers in our substations or the large hydroelectric dams, they have the potential to cause extensive damage.
To minimise the risk of damage to critical equipment, Transpower may work with industry to switch off some parts of the power system for a time in an extreme solar storm. These events are rare, but we are prepared for them and have a plan in place.
If we don’t do this and equipment is damaged, it could require expensive and time-consuming repairs or the total replacement of equipment.