On Tuesday the 19th of August between 11:45 and 12:20 there was a significant frequency deviation on the mainland. Readings peaked just above 50.2 Hz.
Our quick review of mainland system frequency is charted as follows:
Market Notice 128594 (12:35) informed us that there was a need to vary regulation FCAS requirements to manage frequency.
MARKET NOTICE 128594 ________________________________________________________________________________________________ Notice ID 128594 Notice Type ID Subjects not covered in specific notices Notice Type Description MARKET Issue Date Tuesday, 19 August 2025 External Reference Variation to FCAS regulation lower requirements: NEM Mainland - 19/08/2025 ________________________________________________________________________________________________ AEMO ELECTRICITY MARKET NOTICE Variation to FCAS regulation lower requirements: NEM Mainland - 19/08/2025 FCAS Lower regulation requirements have been increased to manage frequency. The following constraint set has been invoked. F-MAIN_LREG_0400 at 1210 hrs. Manager NEM Real Time Operations
A follow on notice, number 128602 (12:58), informed that the variation had been later cancelled:
MARKET NOTICE 128602 ________________________________________________________________________________________________ Notice ID 128602 Notice Type ID Subjects not covered in specific notices Notice Type Description MARKET Issue Date Tuesday, 19 August 2025 External Reference Cancellation - Variation to FCAS regulation lower requirements: NEM Mainland - 19/08/2025 ________________________________________________________________________________________________ AEMO ELECTRICITY MARKET NOTICE Cancellation - Variation to FCAS regulation lower requirements: NEM Mainland - 19/08/2025 Refer MN 128594. Constraint set F-MAIN_LREG_0400 was revoked at 1245 hrs. Manager NEM Real Time Operations
More to follow in subsequent article(s).
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