Contingency Reserve Quantities

Contingency Reserve Raise and Lower quantities are determined by AEMO according to WEM Procedure: ESS Quantities to maintain the frequency of the SWIS within the Credible Contingency Event Frequency Band set out in Appendix 13 of the WEM Rules

Contingency Reserve Raise 

The DFCM is an offline simulation of the SWIS power system frequency that calculates the quantity of the Contingency Raise offset and Facility Performance Factors for a set of ESS System Configurations comprising following parameters:

  • Underlying System Load;
  • System Inertia;
  • Load Relief Factor;
  • Facility Speed Factor;
  • Largest Credible Supply Contingency; 
  • any other factors that AEMO determines necessary to accurately predict frequency performance for system operations, such as Distributed PV output.

The latest version of the DFCM is available for download below. 





Effective date




From 12/12/2023



This version of the DFCM primarily includes:

  • Addition of DPV axis.
  • Upgrading the DFCM to a Closed-Loop model.
  • Including tau = 0.5 and 1 seconds.
  • Changes to other parameters are available in the explainer within the DFCM file.

From 15/05/2024

Contingency Reserve Lower 

The DFCM is currently used for Contingency Reserve Raise calculation, however, the model is simplified for Contingency Reserve Lower calculation as Facility Speed Factor is not defined for this service. AEMO considers the Contingency Reserve Lower Requirement (CRLR) as below: 


where LCLC is the Largest Credible Load Contingency. The OFFSET, which is produced by Wholesale Electricity Market Dispatch Engine (WEMDE) in a solution file for Primary Dispatch Intervals and Pre-Dispatch Intervals, is a dynamic figure that accounts for:

  • the change in Operational Demand because of an increase in frequency as Load Relief; and
  • the contribution of distributed photovoltaic in response to over-frequency events expected as per AS/NZS 4777:2:2020 – Inverter Requirement Standard.  It is conservatively limited by a fixed cap and includes a large deadband prior to response in the dynamic equation to account for those inverters that might not be compliant against the AS/NZS 4777:2:2020 Standard, hence not responding to over-frequency events.

Margin for Operation 

Margin for Operation is defined as a margin applied by AEMO when determining frequency co-optimised essential system services (FCESS) quantities to account for uncertainty in real time operations. The Margin for Operation used for Contingency Reserve Raise (in the new DFCM) and Contingency Reserve Lower (formula above) are respectively 0.05 Hz and 0.00 Hz. 

Minimum RoCoF Control Requirement

AEMO calculates the Minimum RoCoF Control Requirement under paragraph 5.1.1 of WEM Procedure: ESS Quantities. The associated set of Underlying System Load and System Inertia pairs is available in DFCM output file.

Further Information & Questions

Refer to the WEM Procedure: ESS Quantities for further information.

For any engineering-related queries on DFCM, please contact the WA System Engineering team via

For any WEMDE solution related queries associated with the DFCM, please contact the WA Real-Time Market Monitoring team via

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