Stanwell unit 1 still (mostly) running Fixed Load (Part 2) … but took time for a TTHL test on Wed 6th March 2024

Back on 10th January 2024 I wrote ‘What’s been happening at Stanwell unit 1 since September 2023? (Part 1)’ with respect to a shift to ‘Fixed Load’ bidding apparently to manage some sort of fatigue damage issue in the High Pressure Bypass Valve Pipework (HPBV Pipework) for the unit:

This week two things have happened independently:

1)  Yesterday whilst having an online discussion with someone about our ez2view software, I noticed a large drop in output from one of the 350MW units at the Stanwell corporation that appeared to have been a ‘tip to house load’ (i.e. TTHL) test at the time.  I did not think any more about it, until …

2)  Today I’ve been tagged into a discussion amongst some WattClarity readers and clients with respect to what others have been looking at, in relation to ongoing bidding as Fixed Load.

Not remembering which of the 8 x 350MW units it was that performed the test yesterday, I opened up the ‘Bids & Offers’ widget in ez2view and started at unit STAN-1.  Hey presto, this was the one, as we see here:

With respected to the numbered annotations:

1)  We see the unit drop:

(a)  down to 15MW (i.e. the ‘house load’ for the unit, to cover essential auxiliary services) at the 10:25 dispatch interval

… in the process shifting volume out of ‘Fixed Load’ and to the –$1,000/MWh bid band at the RRN; and then

(b)  Rise again to 365MW at the 13:00 dispatch interval

… increase in output was actually shortly later (i.e. following ramp rates), the 13:00 period was when volume was allocated there.

(c)  Before dropping back to 200MW (from 15:35) and back to Fixed Load bidding (from 19:35).

(d)  Why this is of particular interest is that the TTHL test (if my rusty memory serves me correctly) requires the use of the same HPBV pipework that’s subject to fatigue concerns the past couple of months

… so I am curious about the reasons for the test at this time (e.g. perhaps mandatory at the AEMO)?

2)  Most of the 14-day look-back period shows the unit output consistently at the ‘Fixed Load’ level of 200MW bid.

3)  But we do see some periods (like Fri 23rd February highlighted, but also Mon 26th Feb and Thu 29th Feb 2023) where the unit increased its output, under increased volume in Fixed Load bids, in conjunction with the price spikes.

Posted here today as a rudimentary ‘Part 2’ in this series, and for future reference.