What is system strength?
System strength is a fundamental service required for the power system to operate in a secure state. It is one determinant of how well the power system can return to normal operation following a disturbance or fault on the power system.
System strength in Australia’s electricity system has traditionally been provided by synchronous generators, as an intrinsic by-product of producing energy and reserves. As thermal generators retire or change their operating patterns, the power system will lose system strength and new sources will be required to ensure the power system remains secure.
Transgrid's role in maintaining system strength
Under the National Electricity Rules (NER), we are responsible for meeting specified levels of power system security services in NSW, including ensuring sufficient system strength services are available at all times. AEMO forecasts the required levels of system strength that we are required to provide under two separate means:
- until 1 December 2025, by specifying the minimum fault level requirements and declaring a fault level Shortfall when they forecast that these minimum requirements will not be met. AEMO has identified a system strength Shortfall in NSW from 1 July 2025; and
- from 2 December 2025, by specifying the minimum and efficient levels of system strength required. AEMO’s 2022 System Security Report forecasts the minimum and efficient levels of system strength that we are required to provide.
We have therefore commenced consultation on options to ensure we meet the NER requirements and continue to ensure a safe, secure and reliable power system. We consider that this will enable us to identify the optimal solution to meet both the short-term and long-term needs.
The System Strength Rule Change has established new requirements for connecting parties to meet. A summary of these new requirements can be found on the System strength for network connections page.