This report has been prepared for the Australia Institute to provide advice to the Energy Security Board’s Post-2025 redesign of the National Electricity Market (NEM). The terms of reference require us to examine the arrangements for the provision of inertia and system strength in the NEM.

Inertia refers to the extent to which the power system resists (in micro-second time scales) changes to demand and supply. System strength refers to the extent to which a stable voltage waveform is maintained after disturbances to the system, such as from short circuits or generator failures.

The issues that this paper examines have become a focus for the Energy Security Board in the context of the expansion of renewable generation – which typically does not provide inertia or act as a source of fault current or voltage (i.e. “grid forming) – and the expected future closure of synchronous generation typically obtained from thermal (coal-fired) generation.