Rule Change: Open


This rule change request proposes changes to improve frequency control and system security in the national electricity market. 
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This rule change request proposes changes to improve frequency control and system security in the national electricity market. 

Stable frequency is an important part of maintaining a secure power system. Frequency varies whenever electricity supply does not exactly match consumer demand and uncontrolled changes in frequency can cause blackouts.

Draft determination

On 19 December 2019 made a draft rule to require all scheduled and semi-scheduled generators in the NEM to support the secure operation of the power system by responding automatically to changes in power system frequency. 

The draft rule is designed to address an immediate need for improved frequency control which has been identified by AEMO. The draft rule is intended to commence on 4 June 2020 and sunset after 3 years on 4 June 2023.

Key aspects of the draft rule include:

  • all scheduled and semi-scheduled generators, who have received a dispatch instruction to generate to a volume greater than 0 MW, must operate their plant in accordance with the performance parameters set out in the Primary frequency response requirements (PFRR) as applicable to that plant
  • AEMO must consult on and publish the PFRR, which will specify the required performance criteria for generator frequency response, which may vary by plant type
  • generators may request and AEMO may approve variations or exemptions to the PFRR for individual generating plant.

The Commission invites stakeholder submissions on the draft rule and the draft revised frequency control work plan by 13 February 2020.

The rule change requests

This draft determination relates to two rule change requests, one from AEMO and the other from private individual Dr Peter Sokolowski.

Each of these rule change requests proposed the introduction of a mandatory requirement for all scheduled and semi-scheduled generators to automatically respond to small changes in frequency either side of 50Hz, albeit through different proposed changes to the National Electricity Rules (NER).

The proponents consider that this change to the NER will improve the operational security of the national electricity system and its resilience to system disturbances.

AEMO’s rule change request states that:

  • AEMO is increasingly unable to control frequency in the national electricity market (NEM) under normal operating conditions, due to reduced frequency responsiveness from generation
  • the tools currently available to AEMO cannot effectively control frequency on an ongoing basis, and are increasingly resulting in power system outcomes that AEMO now regards as inconsistent with prudent industry practice.


Alongside the draft rule and draft determination, the Commission also published a notice to consolidate the two rule change requests – Mandatory primary frequency response (ERC0274) and Primary frequency response requirements (ERC0277). The draft determination and draft rule have been made with respect to the consolidated rule change request and named Mandatory primary frequency response.

Frequency control work plan

This rule change is part of our Frequency control work plan which sets out a series of actions that AEMO, the AEMC and the AER are undertaking to review and reform the frequency control frameworks in the national electricity market. 

AEMO has advised that the application of a mandatory obligation on generators to provide primary frequency response will address the immediate system security needs of the power system. 

Through the remainder of the work plan, AEMO and the AEMC intend to improve the incentive arrangements for frequency control and review the appropriateness of the mandatory primary frequency response requirement. 

The draft determination includes a draft revised frequency control work plan.

Related rule change request

On 3 July 2019 the AEMC received a rule change request from AEMO seeking changes to the NER to address disincentives to generators operating their plant in a frequency response mode during normal operation. 

On 19 September 2019 the AEMC commenced consultation on this rule change request (ERC0263  – Removal of disincentives to primary frequency response). On 19 December 2019 the AEMC published a notice of extension, with the draft determination now due by 24 September 2020.


On 19 September 2019 the AEMC published a consultation paper which addressed the issues raised in all three of the rule change requests relating to primary frequency response (ERC0263, ERC0274 and ERC027). Submissions on the consultation paper closed on 31 October 2019 and can be found below.

On 17 October 2019 the AEMC published a revised version of AEMO’s proposed Primary frequency response requirements, which were submitted to the AEMC along with AEMO’s rule change request. In the revised version, AEMO seeks to address concerns that have been raised in discussions with stakeholders. Marked-up and clean copies of the revised document can be found below. 

The revised Primary frequency response requirements document was submitted to the AEMC by AEMO. The AEMC did not have input into the document.

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