Understanding energy
Transmission networks rely on a range of technical factors to operate safely and reliably, so we've broken down some common complex electrical concepts into simple energy explainers. From system strength to inertia, learn why they matter for maintaining a secure power system in Queensland.
What is system strength?
System strength is the transmission network’s ability to maintain stable voltage both during normal operation and when there is a disturbance, like a sudden change in generation or load, or an unexpected electrical fault.
The Australian Energy Market Operator (AEMO) determines the standards for system strength. Under the National Electricity Rules, Powerlink is required to maintain system strength in Queensland’s transmission network.
Synchronous generators – like coal, gas and hydro power stations – provide system strength when they generate. System strength can also be provided by machines called synchronous condensers.
Asynchronous generators – like wind and solar – do not provide system strength and require system strength from another source.
While a system strength shortfall is very unlikely to impact the ongoing supply of electricity to customers in Queensland, it may limit an asynchronous generator's capability to export power to the grid. Queensland has a broad mix of generation types located across various regions in the state which can be accessed through our transmission network in the unlikely event that supply is impacted.
What is inertia?
Inertia is the ability of the system to resist sudden frequency deviations and slow the rate of change of frequency.
The energy required to counter significant frequency deviations caused by an imbalance in power supply and demand during a contingency event can come from either the kinetic energy stored in the momentum of synchronous machines or from an instantaneous, rapid and automatic injection of energy from another source (such as synthetic inertia from a battery).
Similar to system strength, inertia has traditionally been provided by synchronous generators, and additional remediation is now needed to ensure the power system has sufficient inertia to remain secure.
What are NSCAS?
AEMO describes NSCAS as non-market ancillary services that may be delivered to maintain power system security and reliability, or to maintain or increase the power transfer capability of the transmission network. For example, these may include services which can be provided by plant with reactive power absorption capability such as synchronous generators or battery energy storage systems.