Transpower says 'grid emergency' over after power line fault fixed

Thursday, 6 October 2022

The North Island has seen its share of Thursday morning's frosty weather. (Video first published October 6, 2022)

Electricity operator Transpower has withdrawn a grid emergency that it declared in the North Island on Friday morning after power equipment carrying power from the South Island failed at one of the worst possible times.

The fault created a risk of power cuts.

But a spokesperson said shortly after 8am that the emergency was over.

Transpower earlier asked customers and electricity lines companies to save power, but had said if that did not reduce demand sufficiently there could be a risk of power cuts.

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Snow at Waikaia, 40kms north of Gore, on the morning of October 6, 2022.

It had asked households to be mindful of their electricity use to help it “get through this situation”.

“Fortunately we were able to resolve the issue before we had to cut additional demand which would have resulted in some consumers being disconnected,” Transpower chief executive Alison Andrew said.

“We are grateful to those New Zealanders who took action to reduce their usage.”

The state-owned enterprise issued a “customer advice notice” on Thursday cautioning that based on generation offers then, the electricity market would have less than a 200 megawatt buffer to cope with any unexpected outages between 7.30 and 9am on Friday.

That notice was upgraded to a full grid emergency at 5.38am on Friday morning, after the power equipment failure.

A cold snap swept over New Zealand in recent days. Auckland was 5C with southerly winds on Friday morning, while Hamilton was at -2C and Rotorua -3C.

But the emergency warning was triggered by a fault on an HVDC cable which transfers electricity from the South Island to the North Island.

A fault on that infrastructure is one of the worst events that Transpower plans for.

The outage saw spot market electricity prices soar above $100 a kilowatt-hour in the North Island. The normal price is about 10 to 15 cents.

Transpower operations manager Stephen Jay said during the emergency that some power was still flowing across the Cook Strait cable, but a second fault could suddenly stop the flow of electricity.

“The system operator is proactively managing this risk to prevent the risk of cascade grid failure if that second fault were to happen,” he said then.

Transpower worked with electricity lines companies and large industrial customers connected directly to the grid to reduce demand.

The weather is clearing up but it will remain cold for much of the country, MetService forecasts.

During Friday’s brief emergency Transpower advised people to:

Delay putting on a load of washing, using the dryer or dishwasher
Delay charging electronic devices and electric vehicles
Turn off heaters and lights in rooms that you are not using

Andrew said in an interview with Stuff late last month that electricity supply had been tight this winter and could be as tight next winter. “To be honest I would like it to be less tight”.

It had expressed confidence earlier in the week that the market looked likely to cope with the cold weather moving up the country.

Jay said on Thursday that its request then was “part of the normal functioning of the power system” and it didn’t anticipate any impact on consumers’ electricity supply.

But it had warned power companies that based on developments, it could issue a warning notice making further requests for generation, or a grid emergency notice which would let it order lines companies to reduce their demand, for example by remotely switching off ripple-controlled hot water systems.

Genesis Energy spokesperson Estelle Sarney said shortly after the first notice was issued on Thursday that one of the Rankine coal turbines at its Huntly power station was due to be generating electricity on Friday morning.

At that moment, it didn’t intend to increase generation beyond what it had planned but was “constantly monitoring the situation”, she said.

As the country’s two biggest generators of thermal electricity, Genesis and Contact Energy often play a key role in responding to power supply squeezes.

However, Genesis’ coal-powered turbines can take up to 12 hours to ramp up to full generation.