Northland power outage: What we know so far

Many homes and businesses in Northland are without power after a Transpower tower fell near Kumeū about 11am on Thursday.

The region's largest power generator, Northpower, says the outage might last until the end of Friday - or even beyond.

The crisis arose after Northpower lost a major high voltage line into the substation at Maungatapere, a major feed from the grid, which caused much of the region to lose its supply.

A Transpower service provider is on site to assess the damage and determine an expected time when power could be restored.

While no time has been announced yet, some areas are now running on backup generator, however, Transpower says power needs to be conserved until normal supply is up and running.

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By mid-afternoon Transpower said power had been partially restored and some people have already been reconnected. It was not clear how many people this affected.

"Transpower is restoring as much capacity as possible through its lower capacity 110 kV network. However, until one of the larger 220 kV circuits is returned to service there will be insufficient electricity available to fully power the region," the national grid operator said in a statement.

Transpower has been able to reconfigure the power system to provide power including from local sources, such as the geothermal generation at Ngāwhā.

A Grid Emergency Notice lasting till noon tomorrow as an interim period.

"A return to service time for the impacted circuits has not been confirmed."

The tower fell while a second transmission circuit supplying these areas was out of service for scheduled maintenance.

Transpower is also assessing how long it will take to return that circuit to service.

More details will be provided on Transpower's website and Facebook page. Consumers should also check the websites of their retailers and local lines companies for up-to-date outage information.

Outage might last until at least Friday night

Northpower says of its 60,000 customers 50,000 of them are currently without power on thursday evening.

Chief executive Andrew McLeod said power might be out at least until the end of tomorrow but potentially a day or two longer than that. It was awaiting Transpower's confirmation.

It was likely that tonight and tomorrow Northpower would rotate power availability so that customers were on for at least some period of the day, he said.

Northpower had about a third of the power it needed until Transpower system was restored, he said.

There were two lines into the district and Transpower had turned one of them back on but it was relatively small compared to the one that was down.

"We have about 100 megawatts of load all over our network and we can supply about 30.

"What we're doing at the moment is configuring the network to get the critical load, so things like hospitals, we're making sure the refinery's on, we're making sure sewage pumps and things can run and just depending where those critical loads are, you [as a resident] might be lucky enough to be on as well."

Transpower was coordinating with all the power distributors in the region in a combined effort to get as much energy as possible, he said.

"They've got construction crews on site, they've got equipment on site, they're working at pace to really address this tower, that's a big structure down and to get it sorted in a day, or even three days, is pretty impressive."

Once Transpower has informed Northpower when power will be back on line, Northpower will publish clear information on its website about the plan for which areas get power when, he said.

Given that some will not have access to power to look at their computers, McLeod said the company would also be publicising it via radio and hoped that those with power could spread the word to their neighbours who may be without.

McLeod said the national grid was very well maintained and this was an extremely unusual situation and the first time he had heard of a power pylon falling in this way.

What caused the tower to fall?

Transpower says its too early to say.

However, workers were at the site at the time the tower fell.

The area where the tower fell has now been made safe.

There will be a full investigation, but the priority was restoring power to the region.

What to do if you're affected

Civil Defence advises:

Check Transpower's website and Facebook page plus retailers' websites and local lines companies for up-to-date outage information. Turn off your power if you are told to do so. Unplug small appliances as these may be affected by power surges. Don't use candles for lighting as these can cause fires Don't use outdoor/patio heaters or barbecues indoors as these can cause carbon monoxide poisoning Use battery operated radios and use your cellphone sparingly to conserve its power Check in on your neighbours and make sure they're okay