30 June 2023 under-frequency event

This consultation sought feedback on the draft determination of causer for an under-frequency event on 30 June 2023.

The normal frequency band in New Zealand is between 49.8 and 50.2Hz. An under-frequency event occurred on 30 June 2023 when the frequency fell below 49.25Hz because of a loss of more than 60MW injected into the grid.

The system operator recommended that Genesis Energy Limited was the causer of the 30 June 2023 under-frequency event, as the generator that owns Unit 5 of Huntly power station.

Our draft determination agreed with the system operator’s assessment.

No submissions were received on this consultation.

The Electricity Authority's final determination under clause 8.61 of the Elctricity Industry Participation Code is that Genesis Energy Limited (Genesis), as the generator that owns Huntly Unit 5, was the causer of the under-frequency event on 30 June 2023 at 1.42am.

Our reasons for the final determination are:

• An under-frequency event occurred at 1.42am 30 June 2023 when Huntly Unit 5 tripped and frequency dropped to 49.12 Hz in the North Island and 49.22 Hz in the South Island.
• The interruption/reduction of electricity occurred at the grid injection point for Huntly power station, which belongs to Genesis.
• No other asset was identified as having caused or potentially caused the under-frequency event.
• The system operator and Genesis agree that Genesis was the causer of the under-frequency event.

In accordance with clause 8.65 of the Code, the clearing manager will rebate the event charges to relevant participants. The charge advised in the system operator's reports to the Authority was $191,250.

Any dispute of this final determination can be lodged with the Rulings Panel by 5pm on 14 February 2024.