Transpower fined $150K after August 2021 grid emergency causes power outage to 34,000 homes

Power was lost to 34,000 homes on the coldest night of the year in 2021, after a grid emergency was declared. Photo / Mark Mitchell

The organisation responsible for overseeing the country’s electricity grid has been stung with a $150,000 fine after a miscalculation caused a power cut to a section of the North Island during one of the coldest days of 2021.

The switch-off resulted in more than 34,000 households in the central North Island losing power, due to a reduction in wind generation and weed blocking an inlet at the Tokaanu hydro dam, paired with the highest demand for electricity on record.

According to a decision of the Electricity Rulings Panel, around 6.23pm on August 9, 2021, Transpower recorded its “highest demand peak on record” of 7157 megawatts nationwide.

A grid emergency had been declared prior to this point; electricity generators were warned there would be insufficient generation between 5.30pm and 8pm that day.

The panel ruled that a demand allocation notice, sent to distributors asking them to decrease demand at 7.09pm was based on incorrect calculations.

That notice led some generators to switch off power in some areas.

Over the following days, the generators themselves were incorrectly assumed to be responsible for the outages.

Transpower admitted the miscalculation resulted in some customers unnecessarily disconnected and agreed the market impact was “significant”.

It was ordered to pay a $150,000 fine to the Crown, and $6207 in costs.