Tasmania Solo: A Basslink Story

Recently the 500MW Basslink was offline from 24 March to 5 June.  What happened to the Tasmanian electricity market?  We take a look.

Discussion

On 24 March a contractor damaged equipment at a Victorian substation causing Basslink to go offline, and separating Tasmania from the mainland electrically.[i] The fault was initially expected to be rectified by 14 April, but this was subsequently delayed until 31 May and then early June.[ii][iii]  The interconnector finally returned to service at 6pm on Tuesday 5 June – an outage of 3,529 half-hourly trading intervals.

Basslink last experienced difficulties in 2015-16, when a cable fault caused it to be offline from 20 December 2015 to 13 June 2016 – a period of 176 days, or 8,442 trading intervals.  (Almost immediately following the interconnector’s restoration, a non-cable fault caused it to be offline for 36 hours from 22 June until the evening of 23 June.) 

At the time of the outage, dam storages had declined following an extremely dry spring, and there were concerns about Tasmania’s ability to maintain supply.  To address these concerns:

• the 267MW gas-fired Tamar Valley Power Station was recommissioned;[iv]
• three industrial customers were contracted to reduce their load by a combined 140MW;[v]
• 220MW of portable diesel generators were contracted;[vi] and,
• Hydro Tasmania’s cloud seeding programme was brought forward by a month.[vii]

In this latest Basslink outage, the period was much shorter (73 days compared with 176 days) and dam levels going in to the outage were much higher (36.4 per cent compared with 25.8 per cent).[viii] Given the shorter duration and the different time of year (autumn versus summer/autumn), over the outage period dam levels slightly increased by 1.5 per cent, compared with a decline of 12.9 per cent for the 2015-16 incident. However this may be attributable to some significant rain events during the period.  For example the Lake Margaret Power Station weather station recorded 651mm of rain in April and May, compared with a median of 503mm over the past 73 years – an additional 148mm (29 per cent).[ix]

The following table shows a comparison of the outage with the previous corresponding period (PCP) from 2017, and the 2015‑16 Basslink outage.[x]

Source: AEC analysis of NEM Review data

Conclusion

The split of generation during the outage was:

• Hydro: 93 per cent;
• Wind: 6 per cent; and,
• Gas: 1 per cent (the recommissioned Tamar Valley Power Station).

Following Tasmania’s energy security challenges in 2015/16, the Tasmanian Government developed an Energy Security Framework,[xi] to address these risks.  This was successful in meeting the latest outage as, in the light winds of autumn, wind generation’s capacity factor averaged 24 per cent, compared with 39 per cent during calendar year 2017.  Furthermore the analysis of the previous corresponding period showed that at that time Tasmania imported about 11 per cent of its energy from the mainland, again placing more pressure on water supplies.

It is clear that while Tasmania can sustain itself temporarily (and may be better placed to do so with planned developments such as the 112MW Granville Harbour wind farm), in the longer term its participation in the National Electricity Market, perhaps via the mooted Basslink II, is important for Tasmania’s ongoing viability. 

Further discussion is in Matthew Warren’s article, “Texit: What has the NEM ever done for us?”.[xii]

[i] Basslink media statement, Basslink experiences service outage, 28 March 2018

[ii] Basslink media statement, Revision of Basslink’s return to service date, 10 April 2018

[iii] Basslink media statement, Basslink interconnector update, 24 May 2018

[iv] Parliamentary Standing Committee of Public Accounts, Report on the Financial Position and Performance of Government-owned Energy Entities, 1^st August 2017, p.92

[v] Parliamentary Standing Committee of Public Accounts, Report on the Financial Position and Performance of Government-owned Energy Entities, 1^st August 2017, p.96

[vi] Parliamentary Standing Committee of Public Accounts, Report on the Financial Position and Performance of Government-owned Energy Entities, 1^st August 2017, p.20

[vii] Parliamentary Standing Committee of Public Accounts, Report on the Financial Position and Performance of Government-owned Energy Entities, 1^st August 2017, p.97

[viii] Data sourced from https://www.hydro.com.au/docs/default-source/energy-in-storage/storage-summary.xls for the Monday immediately before the date, accessed 6^th June 2018.

[ix] http://www.bom.gov.au/jsp/ncc/cdio/wData/wdata?p_nccObsCode=136&p_display_type=dailyDataFile&p_stn_num=097020&p_startYear, accessed 7^th June 2018

[x] Note that the Previous Corresponding Period has been adjusted so the days of the week align, e.g. 24^th March 2018 was a Saturday, so rather than the 2017 Previous Corresponding Period commencing on 24^th March 2017, it has been adjusted to Saturday 25^th March 2017.  The end date has been adjusted similarly.

[xi] https://www.stategrowth.tas.gov.au/energy_and_resources/tasmanian_energy_security_taskforce/final_report

[xii] https://www.energycouncil.com.au/analysis/texit-what-has-the-nem-ever-done-for-us/