Highlighting particular (frequency and/or AggROT) events through 2024 and 2025

Earlier in 2025, Linton wrote ‘About System Frequency’ to help explain the way in which it’s an instantaneous measure of the balance between supply and demand.

Over the past week, Linton published two analytical articles, looking at instances where the frequency escaped the Normal Operating Frequency Band (NOFB).

1)   On Wednesday 3rd September, Linton posted a trended look of ‘Instances of system frequency outside the normal operating band’:

… which clearly showed the positive impact of the re-introduction of mandatory Primary Frequency Response.

2)  On Thursday 4th September, Linton then followed with a (zoomed-in) tabular listing of ‘Daily NOFB exceedances since 2021’.

It’s the tabular listing we’ll draw further on in this article.

As a measure of the level of imbalance across all Semi-Scheduled units, for many years we have been tracking a metric we define as ‘Aggregate Raw Off-Target’ across all the Semi-Scheduled units that exist at each Dispatch Interval.

On Sunday 24th August, we posted two articles:

1)   firstly, this ‘An updated long-range trend of large instances of Aggregate Raw Off-Target (AggROT) across all Semi-Scheduled units’ … which:

(a)  was an update to the earlier ‘A long-range trend of large instances of Aggregate Raw Off-Target (AggROT) across all Semi-Scheduled units’ as part of the number crunching for for GenInsights Quarterly Updates for 2023 Q4.

(b)  and included 18 months more data (1st Jan 2024 to 30th June 2025) that was not available to the earlier analysis.

2)  which was then followed with ‘An updated tabular list of instances of large AggROT across Semi-Scheduled units’.

It’s the tabular listing that we’ll cross-reference in the aggregated listing below.

At 11:50:35 a frequency of 49.847Hz was recorded.

Note that this date was after 30th June 2025, so not covered in the corresponding tabular record in this article about large AggROT for Semi-Scheduled units. 

As it stands, there are 5 articles currently collated here with respect to 29th August 2025.  Of these, two are of particular relevance:

1)  On the day, we briefly noted a ‘Decay of mainland frequency at lunchtime on Friday 29th August 2025’.

2)  Then ‘More about that decay of mainland frequency at lunchtime on Friday 29th August 2025 (i.e. Part 2)’

… readers might note the form of the decay might suggest something VRE-related in this case?

We will endeavour to provide and collate more here for 29th August 2025 over time.

At 12:06:207 a frequency as high as 50.207Hz was recorded.

Note that this date was after 30th June 2025, so not covered in the corresponding tabular record in this article about large AggROT for Semi-Scheduled units. 

This event was of keen interest to us, for several reasons.  Hence we’ve already started exploring this long-lasted spike in frequency in a series of articles

1)  which appears to have been due, in large part, to some form of glitch in a particular vendor’s supply of self-forecasts (particularly for Solar Farms).

2)  That delivered a very large collective Dispatch Error (hence AggROT) across all solar farms.

(not outside of the NOFB)

Monday 23rd June did not feature in the list of days seeing any instance of frequency outside of the NOFB.

… but checking our record of the AEMO’s 4-second readings, we see the lowest point for frequency on the day was 49.883Hz at 14:55:32

In terms of AggROT, we noted that at the 14:55 dispatch interval, the AggROT = +657MW

(a)  Which lines up with, and suggests contribution to, the lowest frequency point in the day;

(b)  here’s already a number of articles collated here for Monday 23rd June 2025:
i.  Including a note about a ‘New all-time record for NEM-wide wind, on Monday 23rd June 2025’;
ii.  But none highlighting any frequency wobble or large AggROT.

At 15:40:24 a frequency of 49.829Hz was recorded.

In terms of AggROT, we noted that at the 15:40 dispatch interval, the AggROT = +600 MW

(a)  So correlated with, and suggesting contribution to, the frequency drop;

(b)  there’s already a number of articles collated here for Monday 16th June 2025, including two relevant articles:

i.  Starting with ‘Drop in mainland frequency on 16 June 2025’ (in which Linton noted that ‘The low-point was 49.832 Hz, at 15:40:19’; and

ii.  Then ‘Which units show large positive Dispatch Error for 15:40 on Monday 16th June 2025’ … remembering that ‘Dispatch Error’ is a slightly simpler calculation to ‘Aggregate Raw Off-Target’ (but quite related).

(not outside of the NOFB)

9th June did not feature in the list of days seeing any instance of frequency outside of the NOFB.

… but checking our record of the AEMO’s 4-second readings, we see the lowest point for frequency on the day was 49.898Hz at 15:41:16

In terms of AggROT, we noted that at the 15:00 dispatch interval, the AggROT = +688 MW

(a)  So, in this case, not lining up exactly with the daily frequency nadir.

(b)  But noting that we’ve not yet looked at what the frequency was in the 15:00 dispatch interval

(c)  There’s already a number of articles collated here for Monday 9th June 2025 …  but none appear (on quick scan) to be related to this large AggROT, or any potential frequency disturbance.

(commencement of FPP)

Worthwhile highlighting that (in the context of this chronological record) Sunday 8th June 2025 saw the commencement of Frequency Performance Payments, which:

(a)  Changed the method for allocating Regulation FCAS costs and also created a (carrots and sticks) financial incentive for provision of mPFR

… as illustrated in the article ‘Two diagrams to help illustrate the changes coming with FPP (Frequency Performance Payments)’.

(b)  So may be seen as a change point in frequency performance in the NEM?

At 16:15:31 a frequency of 49.840Hz was recorded.

In terms of AggROT, we already noted at the 16:15 dispatch interval, the AggROT = +695 MW

… for this day there are already a large number of articles collated for Monday 26th May 2025, including a number related to the frequency drop (outside of the NOFB) that was triggered by this large instance of AggROT.

(not outside of the NOFB)

24th May did not feature in the list of days seeing any instance of frequency outside of the NOFB.

… but checking our record of the AEMO’s 4-second readings, we see the lowest point for frequency on the day was 49.895Hz at 16:35:15

In terms of AggROT, we noted that at the 16:35 dispatch interval, the AggROT = +616 MW

(a)  So lining up with the frequency nadir

(b)  But there’s not yet any articles exploring this day.

At 14:05:28 a frequency of 49.83Hz was recorded.

In terms of AggROT, we already noted two occurrences:

(a)  These were:

i.  at the 14:20 dispatch interval, the AggROT = +685 MW

i.  at the 14:05 dispatch interval, the AggROT = +834 MW

(b)  For this day we already noted ‘Drop in NEM Mainland Frequency appearing to coincide with trips at New England Solar Farm, on Saturday 19th April 2025’, but have not yet followed any further.

At 13:19:51 a frequency of 50.30Hz was recorded.

In terms of AggROT this did not feature in our list of ‘large’ exceedances…

(a)  and, looking through the dispatch interval data for AggROT, we see that the AggROT was only +87MW in the 13:20 dispatch interval

(b)  so it seems clear that this particular spike in frequency was unrelated to VRE collective over-performance

There’s some articles collated about Friday 11th April 2025, :

(a)  but those there currently don’t appear to be related to this frequency spike.

(b)  It seems strange that we missed this spike at the time, and will have to explore more later

At 16:49:11 a frequency of 49.835Hz was recorded.

In terms of AggROT, we noted already that this day was a special day, with 4 discrete instances of large under-performance in the afternoon.

(a)  These were as follows:

i.  at the 16:50 dispatch interval, the AggROT = +851 MW, which was immediately after

ii.  at the 16:45 dispatch interval, the AggROT = +633 MW, which was 3 dispatch intervals after

iii.  at the 16:30 dispatch interval, the AggROT = +613 MW

iv.  at the 13:45 dispatch interval, the AggROT = +686 MW

(b)  At this point we have only posted ‘Frequency excursion on Monday 31st March 2025’ with the time-range on that chart seeming to line up with the 3 x large instances of under-performance after 16:00.

… so clearly a day to explore in more detail.

(not outside of the NOFB)

19th March did not feature in the list of days seeing any instance of frequency outside of the NOFB.

(a) but checking our record of the AEMO’s 4-second readings, we see the lowest point for frequency on the day was 49.907Hz at 12:51:16

(b)  And, checking the dispatch interval level data, we see AggROT = +329MW at 12:50 and AggROT=+439MW at 12:55

(c)  So some correlation there.

In terms of AggROT, we noted that at the 10:50 dispatch interval, the AggROT = +647 MW

(a)  So not lining up with the lowest frequency point in the day

(b)  And we’ve not yet looked further to see what the frequency was

(c)  Also noting that there’s not yet any articles exploring this day, so this is another one we’ll flag for later analysis.

At 16:14:31 a frequency of 49.839Hz was recorded.

In terms of AggROT this did not feature in our list of ‘large’ exceedances

(a)  checking our Dispatch Interval records, the AggROT was only +32MW for Semi-Scheduled units at the 16:15 dispatch interval

(b) so it seems clear that this particular low point in frequency was  unrelated to VRE collective under-performance

(c) There are three articles currently collated here as pertaining to Wednesday 5th March 2025 in some way.

… in particular in this list we find ‘Afternoon trip of Bayswater unit 3 delivers rapid drop in Mainland Frequency”.

(not outside of the NOFB)

This day did not feature in the list of days seeing any instance of frequency outside of the NOFB.

… and a quick check of the low-point for the day in the 4-second snapshots shows it was 49.885Hz at 13:59:36

In terms of AggROT, we noted that the day saw two discrete instances of collective under-performance:

(a)  These were:

i.  at the 16:55 dispatch interval, the AggROT = +606 MW

ii.  at the 16:35 dispatch interval, the AggROT = +620 MW

(b)  So not lining up with the frequency low point for the day.

(c)  There are a couple articles already collated for Saturday 22nd February 2025, but none looking directly at frequency performance.

(not outside of the NOFB)

This day did not feature in the list of days seeing any instance of frequency outside of the NOFB.

… and a quick check of the low-point for the day in the 4-second snapshots shows it was 49.886Hz at 15:40:20

In terms of AggROT, we noted that at the 15:40 dispatch interval, the AggROT = +602 MW

(a)  So lining up with (and suggesting some contribution to) the frequency low point for the day;

(b)  But there’s not yet any articles exploring this day collated for 21st February 2025 at this point.

(not outside of the NOFB)

This day did not feature in the list of days seeing any instance of frequency outside of the NOFB.

… and a quick check of the low-point for the day in the 4-second snapshots shows it was 49.858Hz at 16:55:32

In terms of AggROT, we noted that this day was a special day, with 4 discrete instances of large under-performance in the afternoon.

(a)  These were as follows:

i.  at the 16:55 dispatch interval, the AggROT = +742 MW

… so lining up with the low point of system frequency on the day.

ii.  at the 16:35 dispatch interval, the AggROT = +752 MW

iii.  at the 16:10 dispatch interval, the AggROT = +849 MW

iv.  at the 15:35 dispatch interval, the AggROT = +626 MW

(b)  Surprisingly, there have been no articles already written and collated with respect to these large instances on 15th February 2025.

(not outside of the NOFB)

This day did not feature in the list of days seeing any instance of frequency outside of the NOFB.

… and a quick check of the low-point for the day in the 4-second snapshots shows it was 49.896Hz at 17:24:24

In terms of AggROT, we noted that at the 17:25 dispatch interval, the AggROT = +708 MW

(a)  So lining up with the frequency low point on the day

(b)  But there’s not yet any articles exploring this day.

At 13:38:24 a frequency of 49.848Hz was recorded.

In terms of AggROT:

(a)  we already noted that at the 13:30 dispatch interval, the AggROT = +686 MW

i.  so occurring occurring two dispatch intervals earlier than the frequency low-point

ii.  And noting that the exceedances on Friday 14th and Saturday 15th February 2025 were larger than this instance

(b)  But looking at the dispatch interval level data, we see AggROT=+559MW at 13:40

… suggesting collective under-performance was one of the factors contributing to the frequency drop.

(c)  it’s interesting to note two articles collated for Thursday 13th February 2025 as follows:

i.  Firstly ‘NEM Mainland Frequency wandering (somewhat more than ‘normal’) on Thursday afternoon 13th February 2025’; and then

ii.   Followed by ‘A closer look at NEM Mainland Frequency (at 100ms cadence) on Thursday afternoon 13th February 2025 (i.e. Part 2)’ .

So this day is one we might delve into more later.

At 16:12:55 a frequency of 49.842Hz was recorded.

In terms of AggROT, this did not feature in our tabular list of ‘large’ instances of Aggregate Raw Off-Target…

(a)  But a quick scan of the dispatch interval data shows AggROT=+569MW at 16:10 and AggROT=+485MW at 16:15

(b)  Which supports the proposition that under-performance of VRE was a significant contributing factor

(c)  There’s no related articles collated here yet  … so we’ll have to look further.

(not outside of the NOFB)

This day did not feature in the list of days seeing any instance of frequency outside of the NOFB.

… and a quick check of the low-point for the day in the 4-second snapshots shows it was 49.897Hz at 18:05:36

In terms of AggROT, we noted that at the 18:05 dispatch interval, the AggROT = +661 MW

(a)  Which supports the proposition that under-performance of VRE was a significant contributing factor

(b)  But there’s not yet any articles exploring this day.

At 14:00:39 a frequency of 49.83Hz was recorded.

In terms of AggROT:

(a)  this did not feature in our tabular list of ‘large’ instances of Aggregate Raw Off-Target…

(b)  A quick scan of the dispatch interval data:

i.  shows AggROT=+79MW at 14:00 and AggROT=+221MW at 14:05

ii.  which (on the face of it) suggests the proposition that under-performance of VRE was not a significant contributing factor in this particular event

(c)  But perhaps not so fast?!

i.  For there’s already quite a few articles collated here, including some articles that do talk about various events at different parts of the day.

ii.  Some of articles (Part 1, Part 2, Part 3, Part 4, Part 5,  Part 6  and Part 8) that do talk to what happened at the 14:00 dispatch interval – including discussions about network outages and action at some VRE.

At 15:42:00 a frequency of 49.842Hz was recorded.

In terms of AggROT, this did not feature in our tabular list of ‘large’ instances of Aggregate Raw Off-Target…

(a)  A quick scan of the dispatch interval data shows AggROT=+93MW at 15:40 and AggROT=-28MW at 15:43

(b)  Which suggests the proposition that under-performance of VRE was not a significant contributing factor in this particular event

(c)  There are currently no articles pertaining to this day collated under this category.

(not outside of the NOFB)

This day did not feature in the list of days seeing any instance of frequency outside of the NOFB.

… but a quick look in the daily stats for frequency in the 4-second data shows the lowest point in the day was 49.87Hz at 17:20:27.

In terms of AggROT, we noted that at the 17:20 dispatch interval, the AggROT = +692 MW

(a)  So aligned with, and being a major contributor to, the frequency drop at the time;

(b)  but there’s not yet any articles exploring 27th Dec 2024.

(not outside of the NOFB)

This day did not feature in the list of days seeing any instance of frequency outside of the NOFB.

… but a quick look in the daily stats for frequency in the 4-second data shows the lowest point in the day was 49.87Hz at 10:40:27.

In terms of AggROT, we noted that this day was a special day, with 4 discrete instances of collective under-performance greater than 600MW:

(a)  These were:

i.  at the 17:05 dispatch interval, the AggROT = +644 MW

ii.  at the 13:55 dispatch interval, the AggROT = +626 MW

iii.  at the 13:25 dispatch interval, the AggROT = +633 MW

iv. at the 10:50 dispatch interval, the AggROT = +601 MW

… so this was ~10 minutes after the lowest point in frequency on the day

(b)  There have already been many articles written about Monday 16th December 2024 (a very hot, stressful, extremely high demand day), but we’d like to particularly flag the following:

i.  Firstly, ‘Where are those Semi-Scheduled Wind Farms in Victoria that were reviewed w.r.t. Monday 16th December 2024’; and

ii.  Then ‘A quick initial review of bids, for Monday 16th December 2024’.

iii.  ‘Further analysis (and more questions) about four VIC Wind Farms on Monday 16th December 2024’

(not outside of the NOFB)

This day did not feature in the list of days seeing any instance of frequency outside of the NOFB.

… but a quick look in the daily stats for frequency in the 4-second data shows the lowest point in the day was 49.882Hz at 15:40:31.

In terms of AggROT, we noted that at the 14:50 dispatch interval, the AggROT = +662 MW

(a) Which was 50 minutes prior to the lowest point for frequency in the day.

(b)  There’s already three articles collated here looking at 14th December 2024

… but none are looking at AggROT and/or frequency.

At 08:09:47 a frequency of 50.158Hz was recorded.

In terms of AggROT, we already noted that this was a special case, with two instances of large over-performance (the only two this size through the year):

(a)  These were:

i.  at the 11:15 dispatch interval, the AggROT = -610 MW

ii.  at the 08:10 dispatch interval, the AggROT = -661 MW

… which is aligned with (and a significant cause of) the frequency spike.

(b)  There have been some articles already published about this day, but (on quick scan) they seem unrelated to these instances.

(not outside of the NOFB)

This day did not feature in the list of days seeing any instance of frequency outside of the NOFB.

… but a reference to the AEMO 4-second data shows the lowest point on the day being 49.891Hz at 14:40:35

In terms of AggROT, we noted that at the 14:40 dispatch interval, the AggROT = +633 MW

(a)  So the two points are correlated in time,

(b)  With the collective under-performance being one of the significant drivers to the frequency drop

(c)  But there’s not (yet) any articles here exploring this day.

At 15:35:35 a frequency of 49.82Hz was recorded.

In terms of AggROT:

(a)  we’d not noted a ‘large’ incidence of AggROT in this tabular record.

(b)  and, checking in on our records for each dispatch interval, we see AggROT=+357MW at 15:35 (i.e. so large collective under-performance, but not large enough to exceed the 600MW threshold I used)

(c)  so we conclude collective under-performance of VRE was a significant (but not the only) driver of this event.

I’ve had a quick look and currently see five articles collated here pertaining to 3rd December 2024

… but none of these seem to explain the frequency drop

At 18:56:36 a frequency of 49.786Hz was recorded.

In terms of AggROT:

(a)  we’d not noted a ‘large’ incidence of AggROT in this tabular record.

(b)  and, checking in on our records for each dispatch interval, we see AggROT=+38MW at 19:00 (i.e. very slight collective under-performance)

(c)  so we conclude collective under-performance of VRE was not the dominant driver of this event.

I’ve had a quick look and currently see two articles collated here pertaining to 22nd November 2024

… neither of them with respect to frequency, or VRE performance

(not outside of the NOFB)

This day did not feature in the list of days seeing any instance of frequency outside of the NOFB.

… but a reference to the AEMO 4-second data shows the lowest point on the day being 49.878Hz at 12:35:32

In terms of AggROT, we noted that in the 12:40 dispatch interval, the AggROT = +642 MW

(a)  So aligned with the drop in frequency;

(b)  But there’s no articles collated here (yet) exploring this day.

At 15:07:11 a frequency of 49.835Hz was recorded.

In terms of AggROT:

(a)  we’d not noted a ‘large’ incidence of AggROT in this tabular record.

(b)  but, checking in on our records for each dispatch interval, we see AggROT=+350MW at 15:05 (i.e. notable collective under-performance, but not above the 600MW threshold set for our filter)

(c)  so we suspect collective under-performance of VRE was one  driver of this event.

I’ve had a quick look and currently see four articles collated here pertaining to 13th August 2024

… including the article ‘Drop in mainland frequency on Wednesday afternoon 13th November 2024’, but this did not explore potential causes.

At 10:45:20 a frequency of 49.791Hz was recorded.

In terms of AggROT:

(a)  we’d not noted a ‘large’ incidence of AggROT in this tabular record.

(b)  and, checking in on our records for each dispatch interval, we see AggROT=+501MW at 10:45 (i.e. significant collective under-performance, but below the 600MW threshold we’d used to filter the list)

(c)  so we conclude collective under-performance of VRE was one significant driver of this event

… but noting there were more factors below

I’ve had a quick look and currently see five articles collated here pertaining to 12th November 2024…

(a)  with this one noting that there were actually 3 separate frequency drops during the day

(b)  the first (at 10:45:20 shown here) was the deepest, and appears to be due to a combination of factors:

i.  Large collective under-performance of Semi-Scheduled VRE to 10:45 ‘weakened’ the frequency stability

ii.  Then there were some trips at Yallourn that tipped the frequency below the NOFB

iii. Clearly food for more analysis!

(c)  But the later frequency dips are also worth exploring later.

At 14:50:27 a frequency of 49.845Hz was recorded.

In terms of AggROT, we saw that at the 14:50 dispatch interval, the AggROT = +629 MW

(a)  On this occasion we posted the article ‘Mainland frequency wobbles, on Wednesday 6th November 2024’  noting the drop noted above.

(b)  This is another to explore more later…

(not outside of the NOFB)

This day did not feature in the list of days seeing any instance of frequency outside of the NOFB.

… and (with reference to AEMO 4-second snapshots) we see that the lowest point in the day was 49.885Hz at 11:17:23

In terms of AggROT, we noted that at the 15:15 dispatch interval, the AggROT = +612 MW

(a)  so not lining up with the lowest point for frequency in the day;

(b)  as it stands, there are two articles collated here with respect to Thursday 24th October 2024 … but neither of them speak to frequency or AggROT.

(not outside of the NOFB)

This day did not feature in the list of days seeing any instance of frequency outside of the NOFB.

… but we note in the daily stats that (according to AEMO 4-second data) the lowest point was 49.852Hz at 15:45:31

In terms of AggROT, we noted that at the 15:45 dispatch interval, the AggROT = +609 MW

(a)  which lines up with the lowest point of the day

(b)  as it happened, we’d noticed the drop in frequency, and had posted:

i.   Firstly ‘Drop in System Frequency (approx 15:45 NEM time) on Saturday 5th October 2024’;

ii.  Then followed up by ‘Drop in System Frequency on Saturday 5th October 2024 – Part 2’.

(c)  So in this case we see that large collective under-performance of VRE was a significant driver of the frequency drop.

At 20:00:16 a frequency of 49.836Hz was recorded.

In terms of AggROT:

(a)  we’d not noted a ‘large’ incidence of AggROT in this tabular record.

(b)  and, checking in on our records for each dispatch interval, we see AggROT=+20MW at 20:00 (i.e. very slight collective under-performance)

(c)  so we conclude collective under-performance of VRE was not the dominant driver of this event.

I’ve had a quick look and currently see four articles collated here pertaining to 23rd August 2024

(a)  with articles speaking about high VRE yield (and curtailment)

(b)  but nothing specifically speaking about the frequency drop

(c)  so one of the days we might drill into further later.

At 18:18:08 a frequency of 49.83Hz was recorded.

In terms of AggROT:

(a)  we’d not noted a ‘large’ incidence of AggROT in this tabular record.

(b)  and, checking in on our records for each dispatch interval, we see AggROT=-24MW at 18:20 (i.e. slight collective over-performance)

(c)  so we conclude collective under-performance of VRE was not the dominant driver of this event.

I’ve had a quick look and currently see only one article collated here pertaining to 19th August 2024

 … with it coincidentally being ‘Tarong North Power Station trips on Monday evening 19th August 2024’.

At 17:46:31 a frequency of 49.818Hz was recorded.

In terms of AggROT:

(a)  we’d not noted a ‘large’ incidence of AggROT in this tabular record.

(b)  and, checking in on our records for each dispatch interval, we see AggROT=-68MW at 17:50 (i.e. slight collective over-performance)

(c)  so we conclude collective under-performance of VRE was not the dominant driver of this event.

I’ve had a quick look and currently see three articles collated here pertaining to 14th August 2024

… of which the key one is ‘System frequency drop with trip at Loy Yang A4 on Wednesday 14th August 2024’.

At 20:15:04 a frequency of 49.821Hz was recorded.

In terms of AggROT:

(a)  we’d not noted a ‘large’ incidence of AggROT in this tabular record.

(b)  and, checking in on our records for each dispatch interval, we see AggROT=-25MW at 20:15 (i.e. slight collective over-performance)

(c)  so we conclude collective under-performance of VRE was not the dominant driver of this event.

We’ve not posted and collated any articles about this day here yet … so this is something to investigate further later.

At 16:12:59 a frequency of 49.812Hz was recorded.

In terms of AggROT:

(a)  we’d not noted a ‘large’ incidence of AggROT in this tabular record.

(b)  and, checking in on our records for each dispatch interval, we see AggROT=-89MW at 16:15 (i.e. slight collective over-performance)

(c)  so we conclude collective under-performance of VRE was not the dominant driver of this event.

We’ve not posted and collated any articles about this day here yet … so this is something to investigate further later.

At 13:21:59 a frequency of 49.779Hz was recorded.

In terms of AggROT:

(a)  we’d not noted a ‘large’ incidence of AggROT in this tabular record.

(b)  and, checking in on our records for each dispatch interval, we see AggROT=-19MW at 13:25 (i.e. very slight over-performance)

(c)  so we conclude collective under-performance of VRE was not the dominant driver of this event.

We’ve already collated a number of articles here about this day here  … and would like to flag that there was simultaneous trip of ER01 and ER02 that triggered this frequency drop.

At 20:50:08 a frequency of 49.835Hz was recorded.

In terms of AggROT:

(a)  we’d not noted a ‘large’ incidence of AggROT in this tabular record.

(b)  and, checking in on our records for each dispatch interval, we see AggROT=+0.1MW at 20:50 (i.e. almost perfectly matching target)

(c)  so we conclude collective under-performance of VRE was not the dominant driver of this event.

We’ve not posted and collated any articles about this day here yet … so this is something to investigate further later.

At 17:59:47 a frequency of 49.799Hz was recorded.

In terms of AggROT:

(a)  we’d not noted a ‘large’ incidence of AggROT in this tabular record.

(b)  and, checking in on our records for each dispatch interval, we see AggROT=-21MW at 18:00 (i.e. very slight over-performance)

(c)  so we conclude collective under-performance of VRE was not the dominant driver of this event.

We’ve not posted and collated any articles about this day here yet … so this is something to investigate further later.

(not outside of the NOFB)

This day did not feature in the list of days seeing any instance of frequency outside of the NOFB.

… but, in referencing the daily stats for this data from the AEMO 4-second data, we see the lowest point on the day was at 49.872Hz at 16:42:20

In terms of AggROT, we noted that at the 14:45 dispatch interval, the AggROT = +605 MW

(a)  So that instance of ‘large’ AggROT does not line up with the lowest point in mainland frequency on the day;

(b)  We’ve not posted and collated any articles about this day here yet … so this is something to investigate further later..

At 19:53:24 a frequency of 49.846Hz was recorded.

In terms of AggROT:

(a)  we’d not noted a ‘large’ incidence of AggROT in this tabular record.

(b)  and, checking in on our records for each dispatch interval, we see AggROT=+58MW at 19:55 (i.e. very slight under-performance)

(c)  so we conclude collective under-performance of VRE was not the dominant driver of this event.

We’ve not posted and collated any articles about this day here yet … so this is something to investigate further later.

(not outside of the NOFB)

This day did not feature in the list of days seeing any instance of frequency outside of the NOFB.

… but, in referencing the daily stats for this data from the AEMO 4-second data, we see the lowest point on the day was at 49.864Hz at 14:14:12

In terms of AggROT:

(a)  we noted that there were two instance on this day:

i.  at the 17:05 dispatch interval, the AggROT = +613 MW

ii.  at the 14:15 dispatch interval, the AggROT = +654 MW

… so this one lining up with the lowest-point for frequency for the day

(b) We’ve not posted and collated any articles about this day here yet … so this is something to investigate further later.

At 12:06:15 a frequency of 50.769Hz was recorded.

In terms of AggROT:

(a)  we’d not noted a ‘large’ incidence of AggROT in this tabular record.

(b)  and, checking in on our records for each dispatch interval, we see AggROT=+33MW at 12:10 (i.e. very slight under-performance)

(c)  so we conclude collective under-performance of VRE was not the dominant driver of this event.

We’ve not posted and collated any articles about this day here yet … so this is something to investigate further later.

At 13:09:59 a frequency of 49.688Hz was recorded.

In terms of AggROT:

(a)  we’d noted noted here the two largest discrete instances of ‘large’ AggROT on the day:

i.  with AggROT at +701MW at 13:35 which followed ~2 hours after

ii.  the larger AggROT at +815MW at 11:40

(b)  Which have already been explored in ‘Aggregate Dispatch Error across all Semi-Scheduled units (NEM-wide) throughout Tuesday 13th February 2024’.

But recall that Tuesday 13th February 2024 saw a ‘Significant Power System Event’ in Victoria, with transmission lines downed etc…

At 17:36:47 a frequency of 49.849Hz was recorded.

In terms of AggROT:

(a)  we’d not noted a ‘large’ incidence of AggROT in this tabular record.

(b)  and, checking in on our records for each dispatch interval, we see AggROT=-96MW at 17:40 (i.e. very slight over-performance)

(c)  so we conclude collective under-performance of VRE was not the dominant driver of this event.

We’ve not posted and collated any articles about this day here yet … so this is something to investigate further later.

(not outside of the NOFB)

This day did not feature in the list of days seeing any instance of frequency outside of the NOFB.

… but, in referencing the daily stats for this data from the AEMO 4-second data, we see the lowest point on the day was at 49.851Hz at 15:24:15

In terms of AggROT, we noted that at the 15:25 dispatch interval, the AggROT = +627 MW

(a)  So we see this lines up with a frequency drop … almost outside of the NOFB;

(b)  We’ve not posted and collated any articles about this day here yet … so this is something to investigate further later.

At 15:17:16 a frequency of 49.793Hz was recorded.

In terms of AggROT:

(a)  we’d not noted a ‘large’ incidence of AggROT in this tabular record.

(b)  and, checking in on our records for each dispatch interval, we see AggROT=-24MW at 15:20 (i.e. very slight over-performance)

(c)  so we conclude collective under-performance of VRE was not the dominant driver of this event.

We’ve not posted and collated any articles about this day here yet … so this is something to investigate further later.

At 09:13:51 a frequency of 49.801Hz was recorded.

In terms of AggROT:

(a)  we’d not noted a ‘large’ incidence of AggROT in this tabular record.

(b)  and, checking in on our records for each dispatch interval, we see AggROT=+188MW at 09:15

(c)  so we conclude collective under-performance of VRE was not the dominant driver of this event.

We’ve not posted and collated any articles about this day here yet … so this is something to investigate further later.