South Australia separates from NEM, again, as interconnector troubles return

Update – As of 8:05pm, the Australian Energy Market Operator has confirmed that South Australia has been re-syncronised with the rest of the National Electricity Market and power flow has been restored via the Heywood terminal.

The South Australian electricity system has again become separated from the rest of the National Electricity Market, with system operator AEMO confirming that the state was again islanded on Monday.

In a notice to the National Electricity Market, the AEMO confirmed that South Australia had separated from Victoria, with the connection between the two states, via the Heywood Interconnector, no longer functioning and electricity is no longer being transferred between the two states.

AEMO told RenewEconomy that they are currently investigating the latest cause of the separation, but the market operator also confirmed that there were no predicted supply shortages within the National Electricity Market.

”The root cause of the separation is currently under investigation by AEMO and the asset owner, AusNet Services,” an AEMO spokesperson said.

“There are currently no Lack of Reserve (LOR) conditions across the entire National Electricity Market.”

In the immediate aftermath of the latest disconnection at the Heywood interconnector, wholesale electricity prices in the South Australian region spiked to more than $5,000 per MWh, and then fell to negative $300 per MWh, as the market operator worked to maintain a balance of supply without the ability to send excess wind and solar generation out of the state.

According to OpenNEM, more than 50 per cent of South Australia’s power was being supplied by solar energy, with an additional 20 per cent being supplied by wind power just prior to the separation.

However, following the latest separation, generation has been cut back from wind generators and large-scale solar projects, with the bulk of generation being supplied by rooftop solar and a ramp-up of gas generators.

There is no immediate threat of interruptions to electricity supplies in either South Australia nor Victoria, but it presents yet another challenge for the energy market operator to maintain supply in a system already facing difficulties flowing from constrained network infrastructure.

South Australia was separated from the rest of the National Electricity Market in the last week of January and remained islanded for more than two weeks.

The January disconnection was caused by damage to the Heywood interconnector and required several of South Australia’s wind farms to be curtailed to manage the supply-demand balance within the state.

The state was reconnected to the rest of the main grid on 17 February.

During the last outage, AEMO assumed control of several of South Australia’s large battery systems and considered the battery systems as the most effective contributors for managing supply security.

AEMO has been contacted for comment. More to come.