As reported in the August issue of CEDEX® Electricity Update, SA peak demands this year were 3.0 GW in summer and 2.5 GW in winter. AEMO states that the state currently has 1.70 GW of combined cycle and steam turbine gas generation and 0.92 GW of open cycle gas turbine generation.

In addition, SA is connected to the other mainland NEM states through the AC, i.e. synchronous, Heywood interconnector, the capacity of which has recently been upgraded to 0.65 GW.

Several years ago AEMO established its Future Power System Security program. In its August 2016 program Progress Report, it explains:

“AEMO established the FPSS program to formalise and accelerate the work it has undertaken in the last few years to address operational challenges arising from the changing generation mix. If left unaddressed, these challenges will test the efficiency and adequacy of current operational and market processes. The FPSS program focuses entirely on power system security. It aims to adapt current processes to address immediate risks, while promoting solutions to maintain power system security over the next 10 years. To date, AEMO has not identified any NEM-wide power system security concerns during normal operation.”

The Report goes on to state:

“Initial challenges are more acute in South Australia, due to the combination of its generation mix and risk of separation from the rest of the NEM. The risk of separation has itself not changed, however, the potential consequences have.”

Related to, but distinct from, this program AEMO has published a number of reports under an agreement with the government of South Australia on issues specific to that state, called South Australian Advisory Function reports.

The August 2016 South Australian Electricity Report contains an extensive discussion of the reliability of supply under circumstances where supply through the Heywood interconnector is lost, including, in the Executive Summary, the following statement:

“In the rare event of the unexpected concurrent loss of both Heywood Interconnector lines, there is a high risk of a region-wide blackout in South Australia. South Australia has separated from the rest of the NEM due to such non-credible contingency events four times since 1999. The likelihood that a region-wide blackout would follow a non-credible islanding event has increased as the region has become more reliant on energy imports, and wind and rooftop photovoltaic (PV) generation, to meet demand.”

It is possible that this, or another statement like it, may have provided a pretext for commentators, unaware of AEMO’s work on system security, to voice doubt and speculation on renewable generation.

Loss of the two Heywood Interconnector lines was not what occurred on 28 September. What did occur, as clearly set out in the preliminary report by AEMO, released on the morning of 5 October, was loss, over a period of 40 seconds, of sections of three of the four major transmission lines running between Adelaide and Port Augusta.

Two of the lines were a double circuit, i.e. two lines on the one set of towers, and this set of towers is the one which most of the published photos show. These lines provide the link between the now closed Northern and Playford coal fired power stations, in the north of the state, and the main load centre, in and around Adelaide.

About two thirds of the state’s wind generating capacity is also linked to major load centres through these lines, as is the Murraylink DC Interconnector.

Should a new link to NSW be built, geography means that it would almost certainly be linked to Adelaide through these lines, or a new line following a similar route. The lines which were damaged constitute a large part of the spine of the South Australian transmission system (the other part being the lines to the south east of the state which form the SA section of the Heywood Interconnector).