Adapting and managing Under Frequency Load Shedding at times of low demand

The following reports outline analysis on adapting and managing under frequency load shedding (UFLS) in the NEM at times of low demand:

• The 2022 Power System Frequency Risk Review provides an update on DER impacts on UFLS (section 3.3.2), UFLS remediation work in South Australia (Section 3.3.3), and UFLS remediation work in other NEM regions (Section 3.3.4).  It also provides an update on AEMO’s analysis around a protected event for the Heywood Interconnector (Section 7.3).

South Australia

• AEMO has completed extensive analysis of non-credible separations of South Australia from the rest of the National Electricity Market (NEM). These studies were undertaken following a recommendation, initially in the 2020 Power System Frequency Risk Review, to request the Reliability Panel declare the non-credible separation of South Australia a protected event under the National Electricity Rules (NER). AEMO has identified a number of preferred management actions which do not require a protected event, and thus has decided not to further progress a request for declaration of the protected event.
• AEMO is collaborating with SA Power Networks to define a new service in South Australia: Emergency Under Frequency Response (EUFR). This service aims to assist in the management of rare, extreme under-frequency events that are traditionally managed with Under Frequency Load Shedding (UFLS). SA Power Networks is seeking complementary services from any proponents that can cost-effectively deliver additional generation increase or load reduction to improve management of these rare events.
• Appendix A of the Final 2020 Power System Frequency Risk Review – Stage 1 explores the impacts of distributed PV on the operation of emergency frequency control schemes in South Australia in periods with high distributed PV generation.
• An update on the progress to address issues identified with the UFLS in South Australia is outlined in section 6 of the Power System Frequency Risk Review – Stage 2 Final Report. This section also includes the proposed scope of the submission to the Reliability Panel for a new protected event relating to the separation of South Australia from the rest of the NEM.
• An updated and expanded constraint set has been implemented to keep imports into South Australia across the Heywood interconnector within limits that reduce the risk of cascading failure and a black system if South Australia separates from the rest of the NEM.
• AEMO is working with SA Power Networks to introduce dynamic arming of the UFLS scheme in South Australia. Dynamic arming, which enables UFLS circuits to be automatically disarmed when they are in reverse flows, is one of a suite of recommendations by AEMO to address issues with UFLS due to the high distributed DPV generation in the region.

Victoria

• In 2023, AEMO published a report that explored dynamic arming options for UFLS for adapting to higher levels of distributed PV, using case studies in Victoria. The report explored options for dynamic arming (reverse flow blocking) of UFLS relays at the sub-transmission 66kV level, distribution 22kV level, or at individual customer sites via Advanced Metering Infrastructure (AMI).
• In 2021, AEMO delivered a report to Network Service Providers in Victoria, outlining analysis on the amount of net load in the Victoria UFLS scheme and impacts of distributed PV. The report highlights areas where action is required to manage growing levels of distributed PV while maintaining an adequate emergency under-frequency response in Victoria.
• In 2023, AEMO delivered an update report with the continuing evolution of UFLS load levels in Victoria during 2021 and 2022.

Queensland

• AEMO has delivered a report to Network Service Providers in Queensland, outlining analysis on the amount of net load in the Queensland UFLS scheme and impacts of distributed PV. The report highlights areas where action is required to manage growing levels of distributed PV while maintaining an adequate emergency under-frequency response in Queensland.

New South Wales

• AEMO has delivered a report to Network Service Providers in New South Wales, outlining analysis on the amount of net load in the New South Wales UFLS scheme and impacts of distributed PV. The report highlights areas where action is required to manage growing levels of distributed PV while maintaining an adequate emergency under-frequency response in New South Wales.