~28 years of history for the VIC-SA interconnector, in one chart

In the preparation of another article pertaining to the introduction of PEC Stage 2 [COMING SOON], we thought it was useful to power up the ‘Trends Engine’ in ez2view and produce the following time-series trends of monthly statistics of Target Flows, and Limits, over the VIC to SA interconnector:

Before getting into the details:

1)  Remember to click on the image if you want a larger resolution image to view in a separate tab;

2)  Those with a licence to the ez2view software can open their own copy of this query here.

With respect to this trend chart, as per the annotations:

1)  Let’s start by looking at the Flow Limits (maximum monthly), in either direction:

(a)  Those ez2view clients who’ve sat in on (or listened to the recordings of) training sessions we’ve provided might recall me saying something along the lines of:

‘I find it easiest to remember that it’s Hobart centric:
(a)  Flow away from Hobart (to the north and/or west) is positive
(b)  Flow towards Hobart (to the east and/or south) is negative’.

… so that principle still holds here for Flow Limits.

(b)  With that in mind:

i.  There’s a couple aberrations in the early years of the NEM that I’m not going to waste time delving down rabbit holes … might be some data/operational glitches?

ii.  But we can clearly see the step up in transfer capability from early 2025 given the early-stage testing and operations on PEC:

>  Prior to this point, the VIC-SA interconnector could commonly be referred to as ‘Heywood’

>  Whereas from this point until the transition to PEC Stage 2, the flow represents Heywood plus PEC Stage 1.

2)  In conjunction with the flow limits, we see the trend of monthly average Target Flow, and three distinct phases of operations:

(a)  Time Range #1 (from January 1999 through until June 2017*)

Over this time-range:

i.  clearly the dominant net flow over most months was from Victoria into South Australia

…  excepting a few months in 2007 and 2008 for reasons we won’t investigate further

… but might be due to the millennium drought.

ii.  that’s a time spread of 18.5 years

iii.  ‘What’s the relevance of July 2017?’, you might ask!  My first thought is that Hazelwood closed at the end of March 2017, and that triggered a significant shift in dispatch and flow patterns across the NEM that took a while to work through.

(b)  Time Range #2 (July 2017 to December 2020)

Over this time range:

i.  there were the majority* of months in which South Australia was a net exporter to Victoria

ii.  There were 29 months with SA net exporting to VIC and 13 months with VIC net exporting to SA

iii.  With the ‘average of monthly averages*’ transfer over that period being –49MW (i.e. flow from SA to VIC)

iv.  That’s a time spread of 3.5 years.

(c)  Time Range #3 (January 2021 to April 2026, with May being incomplete)

Over this time period:

i.  there were the majority* of months in which South Australia was a net importer from Victoria:

ii.  Specifically, 43 months with SA net importing from VIC and 21 months with SA net exporting to VIC

… so the reverse of the pattern of mid-2017 to 2020

iii.  And also the ‘average of monthly averages*’ transfer over that period being +44MW

… i.e. net exports from VIC into SA again (though not as dominantly as for the first 18.5 years)

… which is roughly the reversal of the 3.5 years mid-2017 to the end of 2020

iv.  This was a time spread of 5.3 years.

3)  Bumped onto the end of Time Range #3 is the jump in transfer capacity (temporarily allocated to VIC-SA prior to PEC Stage 2) for PEC Stage 1

(a)  Earlier articles noted various stages … for instance:

i.  On 11th Oct 2024 we noted ‘Testing the Heywood interconnector on Friday 11th October 2024, as part of PEC Stage 1’

ii.  And on 28th Jan 2025 Allan wrote ‘PEC Stage 1 in operation – be careful what you wish for’

(b)  There’s more articles about Project Energy Connect:

i.  Collated in this Project Energy Connect (PEC) category here.

ii.  and/or tagged with Project Energy Connect (PEC).

4)  Worth readers remembering that all of the above ignores the patterns over the (smaller, DC) Murraylink interconnector.

5)  Finally, in terms of price differentials:

(a)  Of the 328 months in the data range:

i.  188 months (57% of the total) saw at least one instance of SA prices higher than VIC prices by more than $1000/MWh

ii.  Of those, 97 months (30% of the total) saw at least one instance of SA prices higher than VIC prices by more than $10,000/MWh

(b)  Of the 328 months in the data range:

i.  126 months (38% of the total) saw at least one instance of VIC prices higher than SA prices by more than $1000/MWh

ii.  Of those, only 13 months (4% of the total) saw at least one instance of VIC prices higher than SA prices by more than $10,000/MWh

… though readers should not forget that ‘hanging off the other end’ of VIC are both NSW and TAS (which provides much more insulatioN)