Last Friday (5th September 2025) we’d written about ‘AEMO notes ‘New Victorian system normal constraint to manage contingency size on north-west Victoria’’, in which:
- We flagged the new ‘V_NWVIC_GFT1_750’ constraint equation ;
- Which has become invoked from 10:00 (NEM time) on Tuesday 9th September 2025.
Curiosity prompted me to (temporarily) configure a new alert in the ‘Notifications’ widget within ez2view to let some of us know when this new constraint equation bound (with Marginal Value greater than $10/MWh) – and, lo and behold, a little over 24 hours since being introduced that alert flagged for the first time:
As we can see here, the alert triggered at 19:16 (NEM time) on Wednesday 10th September 2025 for the 19:20 dispatch interval. Now with the benefit of ‘Next Day Public’ data we can use ‘Time Travel’ in ez2view to have a quick look at yesterday evening:
In this image:
1) I’ve mashed together two widgets in this window:
(a) the ‘Constraint Dashboard’ widget (focused on this constraint)
(b) and the ‘Unit Dashboard’ widget (focused on ARWF1, which is one of the units on the LHS of this constraint)
2) I’ve shifted the time context in two ways:
(a) I’ve time-travelled the whole window back to 22:00 yesterday (by which time the constraint had un-bound)
(b) but have also set the tabular views to look at the 19:20 dispatch interval.
3) In general terms, we can see that the LHS (left hand side):
(a) is entirely populated with Wind Farms
(b) five of them, located in north-western Victoria (as flagged in the earlier article), with uniform LHS factors of +1.0
… so each equally constrained when the constraint is bound, assuming they all bid the same.
4) For this interval, we can see that:
(a) The ARWF1 unit was slightly constrained down by this constraint
(b) With 201MW available and 195MW target (i.e. 6MW ‘constrained down’)
(c) As a result of its marginal bid being at -$148/MWh at the RRN …
5) As a result of which, the auto-bidder deployed on the unit shifted volume down the price stack, to try to avoid more constraint.
No doubt we’ll see this constraint equation feature again…
A quick look back at combined availability levels for the affected wind generators shows that this constraint could bind about 10% of the time. The energy potentially curtailed might be something like 2.5% of available output. Not insignificant.
In practice the figures will be something lower because of other constraints and price-based offloading.