Security and reliability
In this section
In this section
- Ancillary services causer pays contribution factors
- Network support and control ancillary services procedures and guidelines
- System restart ancillary services guideline
- Market ancillary services specification and FCAS verification tool
- Regional benefit ancillary services procedure
- Frequency and time deviation monitoring
- Load relief
As the independent market and system operator for the National Electricity Market, AEMO has key responsibilities to maintain system security and reliability in accordance with standards defined in the National Electricity Law, National Electricity Rules (NER) and also by the AEMC’s Reliability Panel. The AEMC also provides an overview of security and reliability on its website.
Power system security relates to the ability of the power system to continue operating within defined technical limits (satisfactory), even in the event of the unexpected disconnection of a major power system element such as an interconnector or large generator (secure).
AEMO’s responsibilities, detailed in clause 4.3.1 of the NER, are to be achieved in accordance with the power system security principles, described in clause 4.2.6 of the NER. These principles include:
- In normal operation, operating the power system so it remains in a secure operating state to the extent practicable.
- When a contingency event occurs, taking all reasonable actions to adjust the conditions of the power system, where possible, with a view to restoring a secure operating state as soon as reasonably practicable.
- Arranging for emergency frequency control schemes to respond to unforeseen events whose impact exceeds what would normally be considered credible.
Key elements that affect the maintenance of power system security include:
- Frequency control
- Voltage control
- System strength
These key elements are outlined in the Power system requirements paper (779 KB, pdf).
Power system reliability relates to the probability that the installed capacity to produce and transport electricity (including generation and demand response), will be sufficient to meet the actual or anticipated demand for electricity.
The NEM is considered to be in a reliable state, under NER clause 4.2.7, when:
- No load has been disconnected or is expected to be disconnected by AEMO.
- No load shedding is occurring or is expected to occur.
- AEMO reasonably believes the power system is meeting, and will continue to meet, the reliability standard.
The reliability standard (clause 3.9.3C of the NER) is defined as a maximum percentage of energy unserved by generation and interconnector capacity, as a percentage of total energy demanded in a region over the financial year and is set at 0.002%.
In performing its responsibilities that require power system reliability assessment, AEMO applies the reliability standard in accordance with the Reliability Standard Implementation Guidelines. These include the publication of planning and forecasting assessments spanning long-term, medium-term and operational timeframes.