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NEM Constraint Methodology
How Network Map turns AEMO's public constraint data into the constraint views in Markets.
Data Sources
The constraint views are derived from public National Electricity Market data published by AEMO, including dispatch constraint results, constraint equations and constraint set invocations, together with Network Map's own transmission network data.
Key Concepts
| Term | Meaning |
|---|---|
| Constraint equation | A linear limit used in dispatch: a left-hand side (a weighted sum of generator, load and interconnector terms) must stay within a right-hand side limit |
| Binding | A constraint is binding in an interval when dispatch is held at its limit |
| Marginal value | The change in total dispatch cost if the constraint's limit were relaxed by 1 MW; higher values mean a more costly constraint |
| Constraint set | A group of constraint equations invoked together, usually for a network outage or system condition |
| Utilisation | How close a constraint's left-hand side is to its right-hand side limit over time |
On the Map
Where a constraint can be associated with transmission lines, the Constraints view draws it on the map so you can see where the network binds and how often.
The Free Live Constraint Map
Network Map's public NEM Transmission Constraint Map has been free since February 2025 and is updated every 5 minutes from AEMO dispatch (DISPATCHIS) data. Open it, switch on Transmission Constraint Map in the sidebar, and select any line to see its constraint utilisation history. The full constraint suite, with constraint sets, equations, marginal values and investigation, is in Network Map Markets.
