Which units show large positive Dispatch Error for 15:40 on Monday 16th June 2025

Earlier today, Linton’s posted the article ‘Drop in mainland frequency on 16 June 2025’ with respect to a drop in mainland frequency (outside of the NOFB).  Linton wrote:

‘(c)  A pattern of slowing-then-recovering cycles appears:

i.  15:25  to 15:28 (3 mins, in the leadup to our zoomed-in chart)

ii.  15:28 to 15:33 (5 mins)

iii.  15:33 to 15:37 (4 mins)

iv.  15:37 to 15:44 (7 mins), the last one included the nadir.

(d)  Frequency spent close to a minute at or near the lower NOFB, between 15:40 and 15:41.’

So it’s the 15:40 dispatch interval (NEM time) that’s most of interest to us, given that this is the one in which the frequency dropped to the lower bound of the NOFB, before dropping under just afterwards.

With the ‘Notifications’ widget inside of ez2view and the use of Time-Travel back to 15:40 we can quickly establish (across all units) which units had the largest positive Dispatch Error within this Dispatch Interval (because a positive Dispatch Error is what we don’t want in this particular context, in relation to supporting frequency):

Note that:

1)  I’ve set the alert tolerance to any unit with a Dispatch Error >25MW in absolute terms, so the list appears on the page without scrolling; and

2)  I’ve highlighted the large positive Dispatch Error:

(a)  Semi-Scheduled units in Green

(b)  Scheduled units in Blue.

Low and behold … most are Semi-Scheduled VRE units:

1)  Which is not a surprise

2)  Which does point back to our ongoing question ‘Is the Semi-Scheduled category scalable, or sustainable?’.

3)  increasingly we (and others) think the answer is NO.