Power system operation

Security of supply is a measure of the power system's capacity to continue operating within defined technical limits, even in the event of the disconnection of a major power system element such as an interconnector or large generator.

Reliability is a measure of the power system's capacity to continue to supply sufficient power to satisfy customer demand, allowing for the loss of generation capacity.

AEMO's system operating procedures are developed primarily for AEMO to provide information related to the management of the National Electricity Market (NEM) and security of the power system.

Guidelines for preparing Local Black System Procedures

Clause 4.8.12 (e) of the National Electricity Rules requires AEMO to develop and publish guidelines for preparation of local black system procedures in consultation with Generators and network service providers.

Scope of Delegations to TNSPs

AEMO has the power to delegate to TNSPs some of the AEMO power system security responsibilities under clause 4.3.3 of the National electricity Rules. The linked page below has details of the delegations made to a number of TNSPs in the NEM.

Reserve Level Declaration Guidelines

An LOR declaration alerts Registered Participants to a probability of capacity reserves being insufficient to avoid load shedding (other than interruptible load) given reasonably foreseeable conditions and events.

These are the reserve level declaration guidelines made under clause 4.8.4A of the National Electricity Rules (Guidelines).

These Guidelines  describe the considerations and methodology AEMO applies in deciding to declare an LOR condition, and the levels of LOR conditions that may be declared.

August 2023 review of the Guidelines

Under Clause 4.8.4A of the National Electricity Rules (NER), the Reserve Level Declaration Guidelines (RLDG) must be reviewed by AEMO at least once every four years. The last time these Guidelines were reviewed was in December 2018.

AEMO has recently undertaken a review of these Guidelines and is not aware of any material issues with the interpretation or application of the current RLDG.
However, in 2021-22, AEMO identified the need to amend the RLDG and several other AEMO instruments to implement the ST PASA Replacement Project (AEMO | ST PASA Replacement project). A rule change was made in 2022 to facilitate this project, effective from 31 July 2025. AEMO is currently targeting consultation on these instruments commencing in 2024 and intends to include a review of all aspects of the RLDG within the scope of that consultation.

Power System Operating Procedures

Distributed Photovoltaics (DPV) Contingency and / or Minimum System Load market notice framework

AEMO has implemented a market notification framework to increase transparency on actions taken to maintain power system security, and seek a market response where possible, during challenging system operating conditions coupled with high rooftop solar PV exports.

These new market notifications will support market development and better communicate power system risks and the operational response, while industry also works on future solutions to better integrate Distributed Energy Resources and drive consumer participation in emerging and new markets.

AEMO’s new framework, similar in concept to the Lack of Reserve (LOR) process, consists of three Distributed Photovoltaics (DPV) Contingency and / or Minimum System Load market notices:

1: Forecast potential Contingency or Minimum System Load event and seeking a market response.

2: Advise action has been taken to maintain system security, such as recalling planned transmission maintenance outages, increasing electricity demand by directing scheduled load into service or curtailing large-scale generation.

If these measures are not sufficient, then as a last resort AEMO instructs the relevant NSP to maintain demand or rooftop solar within thresholds. This could result in curtailing small scale solar PV via the DNSP.

3: Notify that curtailment of rooftop solar PV is occurring as a last resort because preceding actions have not been sufficient to maintain power system security

In activating this framework AEMO’s control room will communicate directly to TNSP control rooms. If the action to maintain system security falls under the purview of the distribution network, DNSPs will determine how demand is maintained and this may include curtailing rooftop solar where this capability is available.