Yesterday (Tuesday 13th May 2025) 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.
Note that:
1) As noted earlier, the the ‘N-CTYS_3L_WG_CLOSE’ constraint set (which we have seen before), containing the ‘N::N_CTYS_2’ constraint equation, is still invoked for this afternoon and evening
2) Which could be a driver to possible volatility later this evening (Wednesday 14th May 2025).
So as Part 2 in an emerging Case Study, I’ll just attach this snapshot from the ‘Bids & Offers’ widget in ez2view time-travelled back to the 16:25 dispatch interval (i.e. which is 2 dispatch intervals before the 16:35 dispatch interval at which the first >$10,000/MWh spike was captured) which, with the benefit of ‘next day public’ data sets, focused in on the TUMUT3 unit:
Highlighted on the image are two simultaneous changes in the bid:
1) There was a large volume of capacity (1,754MW) moved from higher-priced bands down to the –$1,000/MWh Market Price Floor band at the RRN…
(a) Which resulted in the dispatch target increasing to 1,754MW for the unit in that dispatch interval (the prior target had been 265MW (not shown on that image), with the unit reaching 264MW as FinalMW for the prior interval … or InitialMW for this interval);
(b) This part of the rebid occurred at the same time as…
2) There was a sizeable reduction (-82MW/min) in ROCDOWN rate for the unit, down from 100MW/min to 18MW/min.
Now, before any reader gets on their high horses with claims about this type of rebidding behaviour, note that this has been well discussed over years (indeed decades!) past – so my aim in publishing here is to help people to understand, rather than to point out any potential wrongdoing (there is none) or other skulduggery.
It will help set some context to the parts of this Case Study to come…
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