Market Review: Completed


On 6 April 2023, Reliability Panel published a final determination and revised standard for its review of the Frequency operating standard (FOS) that applies in the national electricity system.
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On 6 April 2023, Reliability Panel published a final determination and revised standard for its review of the Frequency operating standard (FOS) that applies in the national electricity system. 

The key elements of the revised FOS are:

  • the introduction of system limits for rate of change of frequency (RoCoF) following contingency events
  • changes to the settings that relate to the limits and thresholds for contingency events
  • changes to the FOS that applies during system restoration following a major system disturbance
  • confirmation of the allowable ranges for frequency during normal operation, the primary frequency control band (PFCB) and that the target frequency as 50 Hz
  • the removal of the limit for accumulated time error.

In the context of the decarbonising power system, the Panel's determination supports the long-term interests of consumers by balancing the benefits of a secure and resilient power system with the costs of achieving this.

The revised FOS will take effect from 9 October 2023. This date aligns with the commencement of the new market ancillary service arrangements for very-fast contingency FCAS, which provide fast frequency response.

The Panel’s determination is supported by expert technical advice from AEMO, in accordance with the NER, and complimentary advice provided by GHD.

Key dates for the review

The terms of reference require that the Panel completes this review by 7 April 2023.

Publish issues paper and terms of reference 28 April 2022
Public forum - Initiation May 2022
Close to submissions to the issues paper 9 June 2022
Receive AEMO advice 30 September 2022
Publish Draft Determination 8 December 2022
Public forum – Draft Determination 15 December 2022
Publish Final Determination 6 April 2023
Proposed implementation date for the revised FOS 9 October 2023


The FOS defines the range of allowable frequency for the power system under different conditions, including normal operation as well as after events that occur that can impact the power system. Specifically, it defines the frequency bands and timeframes:

  • in which the system frequency must be restored following different events, such as the failure of a transmission line or separation of a region from the rest of the NEM. 
  • which are referred to by the performance standards that apply to generator and network equipment in the NEM.

Under the National Electricity Rules (NER) the Panel is responsible for determining the power system security standards, including the FOS that apply to the national electricity market (NEM). These standards govern the maintenance of system security and reliability in the NEM; both the mainland NEM and Tasmania.

The frequency operating standard for the mainland NEM and Tasmania was last reviewed and determined by the Reliability Panel in 2019.

Consultation on the review commenced on 28 April 2022 with the publication of an issues paper outlining a number of issues for consideration in relation to the control of power system frequency. The Panel published a draft determination on 8 December 2022 and invited stakeholder feedback on proposed changes to the FOS. 

This review of the FOS is part of a broader program of regulatory reform relating to essential system services that progresses the Energy Security Board’s (ESB) recommendations in the post-2025 work. The review of the FOS is related to the frequency control element of the ESB’s essential system services workstream to “strengthen the grid” and support power system security. 

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