South Australia re-connected to main grid as AEMO completes delicate operation

The South Australia electricity market has been re-connected to the main national grid after the Australian Energy Market Operator completed a delicate operation to “resynchronise” the state using a temporary single line that was completed in little more than two weeks after ferocious storms tore down the main link with Victoria.

The re-connection appears to have been completed around 1605 AEST (5pm AEDT, as the grid does not operate on daylight saving time) and took around two hours to complete.

South Australia was abruptly cut off from the main grid around 1.35pm on Friday, January 31, when a storm flattened at leat six massive transmission lines that tore down the 500kV line that links Latrobe valley with the Portland smelter in south west Victoria, and then South Australia.

Despite the potentially huge impact of the event, the lights did not go out in South Australia, thanks largely – according to engineers at AEMO – to the quick and anticipated reaction from the state’s wind farms, solar farms, rooftop solar and battery storage.

The wind farm, and some solar farms, almost instantly reduced their output to deal with a surge in frequency (South Australia had been exporting nearly 500MW of excess output to Victoria at the time of the separation). The state’s three big batteries also played a key role by quickly ramping up to add load to the system, and then changing  direction when needed to deal with frequency variations.

See: Wind and batteries saved the day when storm cut South Australia adrift

Remarkably, over much of the 16 days that South Australia was separated from the main grid the state still operated at more than 50 per cent renewables for much of the time, and for the first 12 days delivered cheaper wholesale prices than most other states.

However, a drop off in wind output over the last few days reduced the share of renewables, and delivered more pricing power to the gas generators that quickly bid up the price. The price surged even higher immediately after the re-connection to Victoria.

(South Australia was considered to be operating as an island, even though the smaller MurrayLink remained in operation. However, MurrayLink is a DC interconnection and does not provide system strength, so AEMO treated South Australia as an island even though it could deliver a small amount of exports, or accept a small amount of imports).

To add to the complication, the South Australia grid also had to accommodate the massive Portland smelter, which found itself on the South Australia side of the network separation. After being re-energised after the initial transmission break, the Portland smelter was powered by the nearby Mortlake gas generator in Victoria, but its attachment to South Australia complicated the management of the S.A. grid.

On Monday afternoon, the MurrayLink was reduced to zero output as AEMO went about the delicate task of re-connecting the two states and “resynchronising the two grids”. It sought expert advice from the main grid operators, and Tesla engineers, to help plan the procedure.

AEMO has since informed the market that the special directions imposed after the January 31 event have been rescinded, although the state will continue to rely on just one circuit to Victoria while another temporary circuit is added in a few weeks time. Full repairs to the damaged transmission line may take up to a year.

The state’s three big batteries – at Hornsdale, Dalrymple North and Lake Bonney have been allowed to resume market trades after being required by AEMO to rest at a certain hold point and in reserve. AEMO considered the batteries to be the sharpest tool in their box should anything go wrong while South Australia was operating as an island.

See: AEMO takes control of S.A. big batteries to help manage isolated grid

The Portland wind farm, near the smelter, has also been allowed to resume production, and it is assumed that other wind farms impacted by the outage – Lake Bonney and Canunda in South Australia and Macarthur in Victoria – will be allowed to resume production too.

Note: Corrects time of resynchronisation in earlier version.