Amendments to the Inertia Requirements Methodology

Key changes

AEMO received five submissions in response to its issues paper, with a range of views on the proposal. AEMO thanks stakeholders for their submissions and appreciates the thoughtful contributions on these complex matters.

After considering first stage submissions, AEMO has issued a draft Methodology for further consultation. The draft Methodology reflects AEMO’s draft determination as follows:

• NER requirement: system-wide inertia level and inertia sub-network allocation – AEMO will base the sub-network allocation on the individual inertia sub-network requirements and will vary the total amount of inertia in its power system simulation studies to determine the system wide level of inertia
• NER requirement: process for determining sub-network islanding risk – AEMO will consider the list of factors in the new NER clause 5.20B.2(d) when forecasting and determining the likelihood of sub-network islanding, and factors relating to evidence from historical islanding events.
• NER requirement: inertia network services specification – AEMO has included the inertia network service specification as part of the draft Methodology, drawing from its voluntary standard and test specification for grid-forming inverters published under the Engineering Framework to inform the specification for synthetic inertia providers.
• Methodology improvement: additional modelling considerations – AEMO will update the Methodology to explicitly model expected changes in supply, demand, and network assumptions over the 10-year horizon.

AEMO’s draft proposal is to amend the Methodology in the form published with this draft report, with a proposed effective date of 1 December 2024. The 2024 Inertia Report will follow the amended methodology.