Five (re)bids for URANQ12 on on Tuesday 13th May 2025 – Part 3 of a Case Study

On Tuesday 13th May 2025 evening, as it was happening, we quickly noted ‘Late afternoon volatility in NSW (and QLD!) on Tuesday 13th May 2025’ at the start of a period of volatility that was mainly focused on the NSW region.

We decided to piece together a Case Study in a few parts and, as such:

• On Wednesday 14th May 2025 we included a single snapshot of a single rebid for TUMUT 3 in  ‘Part 2 of a Case Study – looking into evening volatility in NSW on Tuesday 13th May 2025’
• This is Part 3,
• with more to come…

In this article we’re going to use a Time-Travelled ‘Bids & Offers’ widget in ez2view to highlight 5 different rebids at the following dispatch intervals (all in NEM time) on Tuesday 13th May 2025:

The 15:30 dispatch interval

For the 15:30 dispatch interval, a rebid received by the AEMO at 09:21 that morning was still in use:

This shows both:

1)  An expectation that, by 16:20, volume would be shifted down to –$1,000/NWh

2)  Which we see is about an hour before the expected price spike (to >$14,000 at 17:35).

The 15:35 dispatch interval

At 15:29 (just prior to Gate Closure #2!) the AEMO received a rebid that ‘reset unit fast start profile SL’ and specifically:

1)  Reduced T1 (i.e. ‘time to synchronise’) by 17 minutes to only 6 minutes

2)  Increased T3 (i.e. ‘time at minimum load’) by 17 minutes to 39 minutes.

One might infer, from this, that (remembering that the unit already had bids down at -$1,000/MWh later in the day):

1)  There was already an expectation of some action a little later on…

2)  This rebid (and others that followed) was about fine-tuning the approach

The 15:55 dispatch interval

At 15:48 the AEMO received a rebid (referencing AEMO’s P5 predispatch demand forecast as the reason) and which

1)  Shifted 150MW from the ~MPC bid band to down at the Market Price Floor bid band at the RRN;

2)  and reduced the ROCDOWN rate (by 8 MW/min) to 3MW/min (similar in style to TUMUT3 in Part 2).

Here’s the view

The 16:30 dispatch interval

At 16:22 the AEMO received a rebid that spoke of plant conditions that allowed for an increase in MaxAvail by 19MW … which contributed to a 23MW increase in volume down at –$1,000/MWh:

The 16:55 dispatch interval

At 16:47 the AEMO received a rebid that spoke to ambient conditions, requiring a small (3MW) drop in MaxAvail:

Remember that there are 4 units at Uranquinty … the approach was slightly different at each unit, but had some similarities.