A final post today to follow my first, second and third earlier with a single snapshot from NEM-Watch at 18:10 today – showing two sequential, large drops in Scheduled Demand for Queensland:
Drop #1 = around 300MW from 17:15 to 17:25; and
Drop #2 = a further 300MW from 17:55 to 18:05.
Now there may be a number of reasons why the demand might have dropped in this way – including the following:
Reason #1) It might have been demand response either, or both:
(a) at large industrial energy users, like some of the ones in Queensland we have been serving for many years;
(b) with aggregated small-scale energy users, like those Reposit have been cheering on in recent days.
however, as noted on the snapshot, prices have been relatively modest in QLD over the past hour or two, unlike earlier – hence spot-price driven demand response seems unlikely.
Reason #2) There are two storm fronts currently passing through South-East Queensland – and this could have affected demand in at least two ways:
(a) provided some welcome relief from the heat and humidity, and so toned down air-conditioning usage; and/or
(b) caused localised (e.g. lightning-caused) distribution network outages (though 300MW would be a pretty large area).
Certainly, as noted, the storms have curtailed earlier than normal the aggregated small-scale PV injection to the grid (given the high penetration rate in South-East Queensland.
Reason #3) There’s also a possible reason flagged in the Market Notice, which talks about a “Non-credible contingency event”, which is AEMO code for something happening that they did not consider “credible” (there’s a technical definition of how that is interpreted in the rules). In this case, it was the trip of a couple transmission lines leading into Brisbane – but:
(a) as noted in the Market Notice below, no bulk disconnection of load was understood when the notice was issued at 17:36; however
(b) the timing of the trip (17:09) does line up reasonably well with the first drop in demand.
Hence, Reason #2 seems most likely. Take-away for the day is that the Scheduled Demand has peaked in Queensland at 15:45 up at the 9,330MW level – when measured on a dispatch target basis (hence not a new record).