17 September 2024 under-frequency event

We are seeking feedback from generators, the grid owner and other market participants who may be substantially affected by an under-frequency event (UFE) on 17 September 2024.

At 2:04pm on 17 September 2024 a UFE occurred when 239.232MW of generation injection was lost at the Huntly grid connection point. This resulted in a drop of frequency to 49.16Hz in the North Island.

The Authority’s draft determination is that Genesis Energy was the causer of the 17 September 2024 UFE because:

• the interruption of energy injected into the grid occurred at Unit 5 of the Huntly power station, which belongs to Genesis
• no other asset was identified as having caused or potentially caused the UFE
• in the system operator’s view, Genesis was the causer of the UFE
• Genesis has accepted that it was the causer.

We welcome feedback on the draft determination and 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.