A major network outage in Victoria on Saturday evening caused the grid in the state of South Australia to “island” or become separate from the rest of the main grid.

The important news is that nothing happened. There was no load shedding, no generator trips that anyone can identify, and the lights did not go out.

Like the last separation that occurred in August 25, 2018, when a lightning strike caused both South Australia and Queensland to separate from the grid, batteries appear to have played a key role in maintaining system security.

They reacted the quickest and initial data suggests that the thermal generators were slow to react. The presence of the batteries – and their absence in key markets such as Queensland – underlines how much more resilient the South Australia grid is, even with more than 50 per cent wind and solar.

According to AEMO, the outage on the main link from Victoria to South Australia, the Heywood interconnector, happened around 6.06pm (NEM time, which is AEST) The reason for the outage is not known and Ausnet, the owner and operator, is investigating. It took several hours for the link to be repaired and back on line.

At the time South Australia was meeting more than half of its local demand from wind and solar, and exporting around 300MW of excess capacity to Victoria, meaning it had more than enough capacity to keep the lights on.

The state had been sourcing 93 per cent of its demand from wind and solar just half an hour earlier, but the solar component had wound back as the sun went down.

The separation meant that some generators had to dial down their output, but the immediate response came from those installations providing FCAS (frequency control and ancillary services) to ensure that the frequency kept in the normal bands, or was quickly brought back.

This appears to have happened, although AEMO have not provided further details. That will come out in a detailed study to be released “soon”. Network wonks can look at a highly technical and data-rich analysis posted on the Watt Clarity website.

What we do notice is that in the flurry of activity after the separation and “islanding”, prices spikes, two diesel generators came on briefly before the prices went negative again. FCAS prices also surged.

An AEMO spokesperson said there was no load shedding, and no directions to any generators. There was a “brief interruption” to the supply at Portland in Victoria, but it is not clear how long this lasted or what its impact was.

In South Australia, which provides more than half of its local demand from wind and solar, supplemented by gas plants and two big batteries (about to be three), and new installations such as the virtual power plant, the market responded as designed. That VPP recently intervened when a Queensland coal generator tripped, helping to maintain frequency at the appropriate levels.

The AEMO spokesperson noted a report in an S.A. paper linking an outage at the Royal Adelaide Hospital to the network problem, but insisted there was no link.