Decision on 14 January 2025 under-frequency event

We recently consulted on the draft determination of causer for an under-frequency event on 14 January 2025.

An under-frequency event occurred at 10.39am, when Huntly Unit 1 tripped and frequency dropped to 49.19Hz in the North Island.

We did not receive any feedback from industry participants on our draft determination.

Our final determination under clause 8.61 of the Electricity Industry Participation Code 2010 is that Genesis Energy Ltd, as the generator that owns Huntly Unit 1, was the causer of the under-frequency event.

The Authority's reasons for the determination are:

a) the interruption of energy injected into the grid occurred at Huntly Unit 1

b) no other asset was identified as having caused or potentially caused the event

c) in the system operator’s assessment, Genesis was the causer of the event

d) Genesis has accepted that it was the causer.

In accordance with clause 8.65 of the Code, the clearing manager will rebate the event charges to the relevant participants. The event charge calculated in the system operator’s report to the Authority is $149,733.40.

Any participant who is substantially affected by this determination may dispute the determination by referring the matter to the Rulings Panel in accordance with clause 8.62 of the Code by 5pm, 17 July 2025.

About the 14 January 2025 under-frequency event

Under-frequency event determinations