Seeking feedback on 21 December 2024 under-frequency event

We are seeking feedback from generators, the grid owner and other market participants who may have been substantially affected by the under-frequency event (UFE) of 21 December 2024.

A UFE occurs when the system frequency falls below 49.25Hz because of a loss of more than 60 megawatts into the grid.

On 21 December, two faults that were likely caused by lightning strikes occurred on the network between Wairakei and Redclyffe, causing both a loss of supply to Hawke’s Bay and disconnecting generation in the region. The reduction of generation and the load demand within Hawke's Bay resulted in North Island frequency dropping to 49.2Hz.

The Electricity Authority’s draft determination is that Transpower New Zealand Ltd as the grid owner is the causer of the UFE.

You can read the reasons in full in our draft determination of causer consultation paper and provide your feedback to compliance@ea.govt.nz by 5pm, Tuesday 8 July 2025

We welcome feedback on both the draft determination as well as the system operator’s calculation of the megawatts of power lost during the event.

All submissions will be considered before a determination on the UFE is finalised.