14 January 2025 under-frequency event

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.

Thanks to all those who engaged with this consultation.

This consultation sought feedback from market participants who may have been substantially affected by an under-frequency event on 14 January 2025.

An under-frequency event occurs when the system frequency falls below 49.25 Hertz (Hz) because of a loss of injection of more than 60 megawatts (MW) into the grid.

At 10:39am on 14 January 2025 an event occurred when 179.787MW of generation injection was lost at the Huntly grid connection point. This resulted in a drop of frequency to 49.19Hz in the North Island.

Our draft determination is that Genesis Energy Ltd, as a generator, was the causer of this under-frequency event because:

• the interruption of energy injected into the grid occurred at Unit 1 of the Huntly power station, which belongs to Genesis
• no other asset was identified as having caused or potentially caused the event
• in the system operator’s view, Genesis was the causer of the event
• Genesis has accepted that it was the causer.

We invited submissions on the draft determination of causer and on the system operator’s calculation of the megawatts of power lost during the event.