What other details are visible, of those network trips in northern NSW yesterday (Fri 7th March 2025)?

Yesterday we noted ‘More network trips in northern NSW, on Friday 7th March 2025 (is TC Alfred involved?)’, and earlier today noted ‘Power Outages in Northern NSW and South-East Queensland at Saturday morning 8th March 2025’.

Curiosity drove me to dig a little further into the network trips noted in the first article, specifically:

• Three separate 132kV AC lines connecting into Mullumbimby (9UG, 9U7 and 9G5)
• All three 110kV DC Directlink lines between Terranora and Bungalora
• and the Lismore SVC.

So, partly as an educational exercise (for myself) I’ve had a look at what I could find…

Essential Energy Network

Grabbing two pages from the Essential Energy DAPR for 2024, we can present two images to highlight where these network elements sit within the Essential Energy (noting not TransGrid) network – starting within Directlink (which is privately owned by APA Group, but connects at both ends to Essential Energy network):

On page 27/165 they write:

‘Zone substations in the Lismore area are spread across both the Coastal and Ranges regions.

The Lismore 132/66kV sub-transmission substation is owned by Essential Energy. It receives its supply via three Essential Energy 132kV lines from the Transgrid 330/132kV sub-transmission substation at Lismore.

A high voltage direct current transmission network is connected between Mullumbimby and Terranora (via Bungalora) which allows supply to be either injected into the Lismore area from Terranora or injected into the Terranora area from Lismore.

A 30MW biomass generator is located at Broadwater and is connected to the Lismore 132/66kV subtransmission substation at 66kV via feeder 0892.’

That’s followed by this image on p28/165:

The three 132kV lines that tripped at 06:12 on Friday 7th March have been highlighted on the image.

Note that the two generators shown in the images above (Broadwater and Condong) are Non-Scheduled* co-gen plant attached to sugar processing in the region.

* note that Non-Scheduled generators generally won’t feature on the LHS of constraint equations:

(a)  though there are some exceptions (e.g. some Non-Scheduled units in South Australia that have more recently been required to operate with Semi-Scheduled characteristics (including being on the LHS of constraint equations and so required to pay attention to Targets if Semi-Dispatch Cap is in play.

(b)  this is relevant to what’s visible in some widgets within ez2view.

With the above in mind, let’s move on….

Any updates in Market Notices?

Within ez2view, the ‘Market Notices’ widget has the ability to search back to the start of the NEM for certain keywords … so this was one of the first things that I looked at:

As we can see …

1)  There’s been no updates from the AEMO via this channel since the trips on Friday morning

…  so we can’t tell (just from Market Notices) whether these network elements are back in service, or not.

2)  But we do note two references to constraint sets, which is a hint to look more into relevant constraint sets….

(a)  MN125356 at 06:44 did highlight the ‘N-X-MBTE_3’ Constraint Set (for 3 x Directlink cables out); and

(b)  MN125357 at 07:27 (shown above) did highlight the ‘N-LS_VC1’ Constraint Set (for the Lismore SVC out).

(c)  But we also note no constraint set noted for the trip of the three x 132kV lines connecting into Mullumbimby (so there’s some lack of visibility there).

What’s visible in Constraint Sets?

Using the ‘Constraint Sets’ widget in ez2view, we filter it down to look at those constraint sets and also some of the network elements in northern NSW and south-east Queensland as follows:

Note that I may have missed off terms I should have included here … but I have included an image of this in the article so the more knowledgeable readers can understand how the filtered Gantt-Chart view comes out looking as it does for the 15:35 dispatch interval:

There’s two widgets shown here:

1)  At the top is the ‘Constraint Sets’ widget in ez2view, filtered as above.  In this we see a number of things, including:

(b)  We see (via the ‘N-X_MBTE_3’ constraint set) that the Directlink cables are expected to be out of service until Wednesday 12th March at 17:00 (NEM time).

(b)  The other thing we can see (via the ‘N-LS_VC1’ constraint set) is that the Lismore SVC was back in service yesterday (i.e. Friday 7th March) afternoon.

(c)  There are other outage-related constraint sets shown, but we’ll not explore them here.

2)  But at the bottom is a newer (still ‘in development’) version of the ‘Congestion Map’ widget, which I have included to highlight two things:

(a)  There’s no Scheduled or Semi-Scheduled DUIDs in the focused area of interest within north-east NSW and south-east QLD (i.e. no dots)…

(b)  … so the only Constraint Equation that is bound that’s really relevant to this article is the ‘N_X_MBTE_3B’ constraint equation, which:

i.  has been invoked because all 3 x Directlink cables are out; and so

ii.  is constraining the Terranora interconnector such that it must flow south and support the load in the northern NSW area.

… as we can see here: