Transpower has extended a precautionary grid emergency notice as a massive solar storm causes concern for networks.
The severity of the ongoing "extreme" G5 geomagnetic storm could impact the power grid, radio signals, and satellite and communications systems, said the US National Oceanic and Atmospheric Administration yesterday.
Transpower said in a statement yesterday morning: "As part of our contingency plan we are removing some transmission lines from service across the South Island as a precaution. In order to do this, we have to issue a grid emergency notice, however this initial action should not impact supply of electricity to consumers."
Some lines in the North Island were later added to the notice.
This morning, the operator issued revisions to the North and South Island formal notices.
Both grid emergency declarations have been extended and are now set to end at 8pm tonight.
They had previously been set to finish at midday.
In the South Island, lines remained out of service at Manapouri, Roxburgh, North Makarewa, Benmore, Islington, Ashburton and Halfway Bush.
In the North Island, lines remained out of service at Huntly Stratford, Hepburn Road, Brunswick, Haywards, Mangamaire, and Whanganui.
Several other circuits have been removed from the North Island notice this morning.
Executive general manager John Clark yesterday told 1News the solar storm induced electrical currents through the Earth.
"Those electrical currents like to use our long transmission lines as an alternative route."
The currents were "not good to have" through the grid so the flow of currents needed to be limited by turning off transmission circuits where possible, he said.
"This is a preemptive measure to make sure other more important equipment, namely transformers and generators, aren't damaged.
"We're able to supply everybody, but we haven't got quite the same level of redundancy in the power system."
The most recent event of similar or greater magnitude occurred in October 2003. That was a G5-level solar storm that wreaked havoc with power globally, notably in Sweden and South Africa where power outages occurred and transformers were destroyed.
The solar storm has also seen aurorae light up skies across the globe.
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