Transpower says grid emergency over, lights should stay on tonight

Thursday, 23 June 2022

Notice issued by Transpower means available supply should still exceed demand, unless something unexpected were to happen.

Transpower is confident the risk of power cuts on Thursday has receded since three pieces of bad luck forced it to declare a “grid emergency” during the period of peak morning demand.

However, it is continuing to report that power supplies are currently looking tight on some days between now and early August, with 12 days when power could be risk if two big things went wrong.

Thursday’s close shave was caused by a mechanical failure at Contact Energy’s Stratford gas power plant, a sudden drop in wind speeds, and a temporary drop in power from one of the five turbines at Genesis Energy’s Huntly Power Station, which together left power supplies short.

Transpower responded by instructing power companies to maximise their available generation and by telling lines companies to turn off ripple-controlled hot water systems in people’s homes.

* Electricity Authority blasts Transpower for role in August power cuts

The state-owned enterprise also advised consumers on Thursday morning in response to a question that it wouldn’t hurt if they turned off unnecessary lighting and delayed charging laptops and mobiles.

But spokesman Nathan Green said it hadn’t resorted to formally advising people to cut back their power usage.

Green said at noon on Thursday that the power market now had a comfortable “buffer” of 440 megawatts of excess generating capacity available to see it through the evening peak.

Transpower had warned shortly before 8am that there was a nationwide risk of power cuts before 9am as there would be insufficient generation if there was any other major unexpected event.

Its “red notice” meant there was insufficient generation to meet expected demand in the event of an “N-1” event, which would be a problem such as one of the five turbines at the Huntly Power Station failing unexpectedly.

It later extended its grid emergency notice to 9.30am so it could work with lines companies to restore controllable load to hot water systems.

Transpower had warned that if the response from power companies was insufficient it might need to “manage demand” by disconnecting power supplies “without further notice”, which would have meant a repeat of the power cuts that occurred on August 9 last year, when power was cut to 34,000 homes.

The danger lifted shortly before 9am, when Green was able to advise that Transpower would be able to get through the morning peak thanks to power companies managing ripple-controlled water systems, unless anything unexpected happened.

Power prices on the spot market spiked to about $1.50 a kilowatt-hour during the grid emergency, which is about 10 times their normal recent level.

Contact Energy said one of the two “gas peakers” at its Stratford plant, each of which are capable of generating more than 100 megawatts of power, had experienced a mechanical fault.

The Stratford plant often plays an important role in helping the country meet periods of peak electricity demand, as it is not reliant on the weather and can normally be turned on and off very quickly.

Transpower warned in May that there was a heightened risk of power cuts on 37 days between June and August, singling out July 26 as a day for another potential grid emergency, but said then that it expected the risks to decrease as the dates got nearer and power companies responded to its warnings.

Energy Minister Megan Woods said the briefings she had so far on Thursday’s emergency indicated “there was no cause for alarm”.

“The issue was that we didn't have a gas peaker come on, so it's not that we don't have enough generation capacity,” she said.

The grid had stood up well and “some of the things that we learned from August 9 last year, we were able to put into play”, she said.

Noting the 440 megawatt buffer for Thursday night, Woods said the lights would stay on and no household would have its power disconnected.