On 5th May, Allan wrote about how ‘Liddell’s ghost stalks the market’ with respect to a series of price spikes in the small hours of Monday May 1st, less than three days after the last Liddell unit tripped offline for the final time.
This followed from the earlier article ‘A second (still rushed) look at volatility in NSW very early on Monday 1st May 2023 … a possible snag with Liddell retirement from market data systems?’.
Today we note that AEMO has provided confirmation about what they have now labelled as Scheduling Error (Incident #54) , with respect to which the AEMO says:
‘When Liddell Power Station was de-registered at 0000hrs on Monday 01/05/2023, the right hand side (RHS) terms in the constraint N>>NIL_33_34 changed to use the default values of 500 MW instead of the correct SCADA value of zero MW. This saw a total of 1500 MW (500 MW x 3 Liddell units) incorrectly being subtracted from the RHS, causing the constraint to bind. To prevent the constraint violating, generation feeding onto lines 33 and 34 was dispatched down and interconnector flow from Victoria to NSW was reduced, resulting in higher prices in NSW. In particular, the constraint lead to six trading intervals with significant price spikes, which saw approximately 173MWh of generation dispatched down.’
They note that the rectification was as follows:
‘The constraint was fixed by changing the defaults RHS values for all 3 Liddell units to 0 from 1200hrs on Monday 01/05/2023.’
More information on AEMO Scheduling Errors is here on their website.