14 January 2025 under-frequency event

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.