21 December 2024 under-frequency event
Consultation
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 below.
Make a submission
The Authority’s preference is to receive submissions in the format shown in Appendix B with "21 December 2024 UFE" in the subject line to compliance@ea.govt.nz by 5pm, Tuesday 8 July 2025.
If you cannot send your submission electronically, please call 04 460 8860 to discuss alternative arrangements.
We will publish all submissions. If you consider that we should not publish any part of your submission, please:
- indicate which part should not be published and explain why, and
- provide a version that we can publish (if we agree not to publish your full submission).
All submissions, including any parts that the Authority does not publish, can be requested under the Official Information Act 1982.