24 January 2023 under-frequency event

We consulted on a draft determination for an under-frequency event (UFE) that occurred on 24 January 2023, when the frequency fell below 49.25Hz because of a loss of more than 60MW injected into the grid. The normal frequency band in New Zealand is between 49.8 and 50.2Hz.

The system operator recommended that the causer was Genesis Energy Limited (Genesis), as the generator that owns Unit 5 of Huntly power station. Our draft determination of causer agreed with the system operator’s recommendation.

We received no submissions to this consultation.

The Electricity Authority's final determination under clause 8.61 of the Electricity Industry Participation Code 2010 is that Genesis was the causer. Our reasons for the determination are:

• A UFE occurred on 24 January 2023 at 3:49pm when frequency dropped to 48.98Hz in the North Island and 49.13Hz in the South Island.
• The interruption/reduction of electricity occurred at the grid injection point for Huntly Unit 5, which belongs to Genesis.
• No other asset was identified as having caused or potentially caused the UFE.
• The system operator and Genesis agree that Genesis was the causer of the UFE.

The charge advised in the system operator's reports to the Authority was $397,118.75 for 24 January 2023. In accordance with clause 8.65 of the Code, the clearing manager will identify the relevant participants affected and the portion of the charges payable to each.

If a substantially affected participant would like to dispute this final determination, they can provide a written notice to the Rulings Panel within 10 business days after the publication of this decision. Notices should be sent to registrar@electricityrulingspanel.nz by 5pm on 12 March 2024