Rule Change: Open
Overview
On 3 April 2023, Grids Energy Pty Ltd submitted a package of rule change requests to improve contingency frequency control ancillary service (FCAS) arrangements in the NEM. The proposals seek to enhance the efficiency of contingency FCAS frameworks by reducing the size of the largest credible load and generation contingency event and making contingency FCAS cost allocation more cost reflective. The requests include:
- ERC0359 - Optimising contingency size in dispatch. This proposal seeks to require AEMO to co-optimise the size of the largest credible contingency during dispatch.
- ERC0360 - Allocating contingency FCAS costs. This proposal recommends adopting a ‘runway’ cost allocation approach to recover contingency FCAS costs.
Consultation paper
On 20 November 2025, the Commission published a consultation paper seeking stakeholder views on the proposal to optimise contingency size in dispatch and allocate contingency FCAS costs through runway cost allocation. Submissions to the consultation paper are due on 18 December 2025.
Background
Contingency FCAS maintains power system frequency stability following disturbances, such as the unplanned loss of a generator, load, or network element, known as contingency events. These services respond rapidly to correct the imbalance in active power caused by such events, arresting frequency deviations and restoring system frequency to approximately 50 Hz.
The timeframe for a draft determination has been extended for both Rule change proposals
On 26 March 2026, the AEMC extended the date for publication of a draft determination for both rule change requests until 4 June 2026 under s107 of the NEL. The extension allows time for the Commission to further investigate stakeholder feedback raised in submissions to the consultation paper.