Some context for the recent Basslink outage

I noted that the recent Basslink outage made the news today as a result of political point scoring in the Tasmanian parliament.

As noted in the news report, the Basslink outage started on Saturday 17th April, and continued through until Monday 26th April.  The NEM-Watch snapshots included in Kim’s post last week showed Basslink flow remaining at zero across the week (on that occasion it could be supposed that Basslink being offline was one of the contributing factors to the price spikes experienced on the mainland).

As some background, here’s the press release issued by CitySpring Infrastructure Trust (the owner of the interconnector) on Wednesday 21st April.

This has prompted me to spend an hour preparing the following analysis from an advanced beta of our NEM-Review v6 product:

1)  Monthly Average Transfers over Basslink

To provide some context to the outage, the following chart shows the monthly average transfers over Basslink (with negative flows representing flows towards Tasmania).

As can be seen, the flow over Basslink has been predominantly towards Tasmania, which can be understood as part of a strategy being employed by Hydro Tasmania to build up reserves of water in its reservoirs by reducing the amount used in these times of low rainfall.

The effect of the 10-day-long outage on the interconnector can be seen as contributing to the halving of average flows over the interconnector for the month of April (up to and including the 27th).

This chart has also been configured to display the monthly average spot prices in VIC and TAS to provide further background to the situation.  As expected, the average prices for both regions tend to track together, most of the time, with prices marginally higher in TAS as a result of the consistent imports from VIC.

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2)  Daily Total Transfers, either way, over Basslink

Providing a little more detail is the following chart, which highlights the aggregate exports and imports (on a daily basis) over Basslink.

As can be seen in this chart, the interconnector has been run hard to support imports into Tasmania for the vast majority of the time it has been operational, but particularly since the beginning of 2008 – with the notable exception of the July-August-September 2009 quarter.

If we “zoom in” to the period since 1st February 2010 through until yesterday, we see that there was a significant decline in imports into Tasmania shown in the 3 week period immediately preceding the outage

We can see a decline in flows in the autumn period for 2009 above, but not as rapid as what was seen in 2010, prior to the outage.

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