5 May 2022 under-frequency event

The system operator recommended that the causer of the 5 May 2022 under-frequency event (UFE) was Meridian Energy Limited, as the generator that owns the Manapouri power station. Our draft determinations agree with the system operator’s recommendation.

In total we received one submission on the draft determination for the 5 May 2022 UFE from Meridian who agreed with our draft determination.

Our final determination, under clause 8.61 of the Code, is that Meridian was the causer of the under-frequency event on 5 May 2022 at 11:41am.

Our reasons for this final determination are:

• a UFE occurred on 5 May 2022 at 11:41am when the frequency fell to 49.21 Hz in the North Island and 48.98 Hz in the South Island,
• the interruption/reduction of electricity occurred when units 1 and 7 tripped at the Manapouri power station,
• no other asset was identified as having caused or potentially caused the UFE, and
• the system operator and Meridian agree that Meridian was the causer of the UFE.

In accordance with clause 8.65 of the Code, the clearing manager will rebate the event charge to relevant participants. The charge advised in the system operator's report to the Electricity Authority is $228,712.50.