02 Jan 2025
Transpower issued a grid emergency notice this morning as it removed some transmission lines from service across the South Island due to the onset of a severe (G4) geomagnetic storm.
This was done as a precaution to prevent damage to equipment and in a way that avoided any impact on consumers’ electricity supply.
The geomagnetic storm has reduced in severity to moderate (G2) and as a result the grid emergency notice has now been lifted.
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.