The Australian Energy Market Commission (AEMC)’s Reliability Panel has made a draft determination that would see updates to the frequency operating standard (FOS) for a more secure and resilient power system for energy customers in the future.

The FOS defines the allowable range of frequency under different conditions and stable operation of the power system requires that frequency be maintained close to the 50Hz target. When generation is equal to demand, the frequency will be stable. However, when there is a mismatch between the demand for and supply of electricity, system frequency will diverge from 50Hz.

Power system equipment, including generators, may disconnect from the power system if the system frequency becomes unstable and changes too quickly, or varies too far from 50Hz, which can in the worst case, eventuate in the collapse of all or part of the power system.

As lower cost, variable inverter-based generation such as batteries, wind and solar displace thermal generators in the system, maintaining stable frequency and operation in the power system is becoming increasingly important.

The draft FOS released by the Panel includes additions and amendments to support power system security and deliver reduced costs for customers in the longer-term. 

The proposed amendments to the FOS include:

  • updated settings for contingency events, including limits on the rate of change of frequency (RoCoF) and the extension of the 144MW Tasmanian generation event limit to also include network and load events
  • confirmation of the allowable ranges for frequency during normal operation, confirmation of the primary frequency control band (PFCB) consistent with the current setting in the Rules and clarification that the target frequency in the national electricity market (NEM) is 50Hz
  • the removal of the limit for accumulated time error, while maintaining an obligation on AEMO to monitor and report on time error accumulation.

The proposed RoCoF limits in the draft FOS would formalise AEMO’s existing operational practices in light of reducing levels of system inertia, helping to manage the risks of contingency events, such as the failure of network infrastructure.

These arrangements would have flow-on benefits, promoting the timely investment of the services, such as synchronous and synthetic inertia, needed to help manage RoCoF after a contingency event. 

They will also support the implementation of new fast frequency response market ancillary services that can be provided by inverter-based technologies such as wind, solar PV, battery and demand-side resources.

The Panel’s determination to confirm the current PFCB settings in the FOS reflects advice from AEMO and GHD that controlling frequency closer to 50Hz delivers value to customers by reducing costs and increasing power system security and resilience. 

The proposed PFCB settings build on the AEMC’s recent rule change to establish a framework to incentivise market participants with frequency performance payments, which comes into full effect on 8 June 2025.

The improved frequency performance also provides a solid foundation to help manage risks to system security as the NEM continues to decarbonise.

The Panel will hold a public forum for the Review of the frequency operating standard on Thursday 15 December between 9:30 am and 11:30 am (AEDT). 

Market participants can register their interest by COB Monday 12 December 2022.

Visit the project page for more information, contact details and details on making a submission. 

Media: Jessica Rich, 0459 918 964,