Transpower has taken precautionary action in the South Island to protect the national electricity grid from a severe solar storm currently affecting Earth.

The company issued a grid emergency notice this afternoon after removing some South Island transmission lines from service due to a powerful G4 geomagnetic storm.

A Transpower spokesperson said the step would not impact electricity supply to consumers but was crucial to safeguard critical infrastructure.

“Removing the circuits from service does not affect electricity supply, but it helps protect vital equipment should the solar storm intensify,” the spokesperson said.

The company said it would issue further updates once the storm had passed or if conditions changed significantly.

Geomagnetic storms occur when the Sun ejects plasma and other charged particles toward Earth in what is known as a coronal mass ejection. While Earth’s magnetic field typically shields against these particles, severe storms can generate unwanted electrical currents in long transmission lines, risking serious damage to transformers and other major equipment.

“To minimise the risk of damage, Transpower may temporarily switch off some parts of the grid during an extreme solar storm,” the spokesperson said. “These events are rare, but we are prepared and have plans in place to safeguard the system.”

Transpower said if equipment were damaged by geomagnetic currents, it could lead to expensive and time-consuming repairs or even require full replacement of vital components.