Why the directions (to 4 units) with 6 coal-fired units still online in Victoria?

We’ve noted this morning that ‘AEMO directs 4 units on in Victoria, to cover System Strength shortfall’ … noting that, at that time, there were 3 coal units in Victoria offline.  Shortly afterwardsL:

1)  we noted ‘Loy Yang A2 joins three other coal units in VIC offline’; and

2)  we speculated the the short-notice outage of Loy Yang A2 was the trigger for the AEMO direction (i.e. dropping number of coal units in VIC down from 7 down to 6).

How often is it that only 6 coal units in VIC are online?

I wondered how often it’s been that the Victorian region had a low of 6 coal units online:

1)  I need to pretty a chart up a bit before publishing,

2)  But the short story is that it’s happened quite often.

So why the direction?

So, we wondered, why the direction (especially for 4 units to replace the System Strength from the ‘missing’ coal units)?

Others have asked the same question – and smarter people than i have pointed to the AEMO document ‘Victorian Transfer Limits Advice – Outages’ (from Oct 2024), and specifically the required combination for direction with an outage on the Moorabool to Sydenham line.   See page 68/87 copied in here, with the 4th row highlighted … which turns out to be the combination of units directed with only 6 coal units online in VIC:

The outage of the Moorabool to Sydenham line

Rounding out this short story is this snapshot from ez2view at the 13:50 dispatch interval (NEM time) with two widgets shown:

1)  At the top is the ‘Constraint Sets’ widget …

(a)  filtered down to constraint sets referencing both network substations

(b)  revealing just one constraint set

2)  The ‘V-MLSY_NOEMTT_R’ constraint set is then expanded in the ‘Constraint Set Details’ widget underneath

… note that we’ve seen this outage before in prior articles here.

We see that this constraint set:

1)  Became invoked yesterday late morning (Wednesday 13th November 2024 at 11:35 NEM time)

2)  Is currently expected to remain invoked out until Wednesday 20th November 2024 at 19:00

That’s all for now…