The extent of the outage. Photo: Supplied
Top Energy says it's aiming to restore power to more than 20,000 affected properties in the Far North progressively by midnight.
The power was cut to more than 23,000 homes and business just after 5.20pm with the outage covering the entire southern part of the district, including the Bay of Islands, Kaikohe, South Hokianga and Whangaroa.
According to Top Energy's outage centre, the fault was on a sub-transmission feeder. Investigations showed half of the 33-kilovolt switchboard was damaged and could not be returned to service on Thursday night.
However, the other half of the switchboard had been salvaged and the company was asking customers to conserve power use until repairs were completed.
A diesel generator was being used at Omania to support the customers in the southern network.
Top Energy workers at Kaikohe substation. Photo: RNZ / Peter de Graaf
A Kaikohe woman living near the substation said she heard a loud boom about 5.20pm.
She went outside to investigate and saw the doors to a building at the substation appeared to have blown open.
Smoke or water vapour was coming out of the doors.
No one was present at the substation so she called 111.
FENZ sent volunteer fire crews from Kaikohe and Ōkaihau.
She said three firefighters entered the building wearing protective clothing and breathing apparatus.
There was no sign of fire that she could see.
The fire crews had left but Top Energy workers continued to come and go from the substation on the outskirts of Kaikohe.
It's exactly the same area that was affected by a huge outage last Friday, just six days ago.
Kaikohe substation provides power to much of the Far North. Photo: RNZ / Peter de Graaf
In that case, the cause was a tree falling on a 33-kilovolt line near Mount Pokaka, south of Kerikeri, but it was not clear why that caused the Kaikohe substation to shut down, cutting power to more than half the district.
The northern part of the district, including Doubtless Bay, Kaitaia, the Aupouri Peninsula and North Hokianga, still has power, in an apparent re-run of last week's outage.
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