3rd January 2006 – Outages force QLD price to VOLL

The week started with commotion in Queensland, when the VOLL price ceiling was reached, as illustrated in NEM-Watch (please click on the image for a larger view):

Please note the following in the above image:

(a) Despite a massive price differential between Queensland and NSW, the Directlink interconnector can be seen to be flowing from NSW into Queensland – which is counterintuitive.
 This was occurring in order that NEMMCO could manage local system security issues in Northern NSW, as indicated in Market Notice #13878, which they published on the day.

(b) Closer inspection of the QNI interconnector will also reveal something strange occurring here – NEM-Watch shows that QNI was flowing north at 418MW and yet its maximum transfer limit was only 323MW in the northwards direction. This can be seen better in the following NEM-Watch chart:

NEMMCO has provided some guidance about why this occurred with the following market notices:

i.  The first Market Notice (#13875), which they published on the day at just after 14:20, refers to the opening of the the NSW region 132 kV feeder 9W2.

ii.  The second Market Notice (#13876), which they published at about the same time, refers to the short notice outage of Lismore SVC following the trip and arc of a Nth NSW 132kV line.

Reference to NEM-Review the day after the event can reveal the following:

The first chart (click on the chart for a closer look) illustrates how there was a loss of about 550MW of generation in Queensland to coincide with this price spike as follows: (a) Millmerran station lost about 350MW of production (further analysis reveals that unit 2 fell offline). (b) Tarong station followed shortly afterwards with the loss of about 200MW of production (further analysis reveals all 4 units reduced output from 350MW to 300MW) Clearly there were stability issues being experienced on the day.  The sudden loss of 550MW of generation would certainly have had an impact.

The second chart (click on the chart for a closer look) illustrates how there was also a sudden drop in demand in Queensland (of about 200MW) to coincide with this price spike.