Investigations into South Australia’s big September blackout have slowed progress on the Victorian interconnector.

The Australian Energy Market Operator (AEMO) was in the final testing phase of a plan to gradually increase capacity on the newly upgraded Heywood Interconnector from 460 megawatts to 650 megawatts.

But AEMO now says its analysis of SA’s September 28 blackout identified a “potential stability issue” when the network is flooded with high power imports and high levels of wind generation.

The market operator is reviewing transfer limits across the interconnector.

Meanwhile, it will limit flows from Victoria to SA to 600 megawatts.

Exports to Victoria are capped at a maximum of 500 megawatts.

The September blackout was caused by tornadoes that cut transmission lines in the state's mid north.

This set off a catastrophic chain of events that overloaded and shut down the state’s power network.

The ensuing debate about South Australia’s energy mix has seen a lot of blame heaped on the reliance on renewable sources, though South Australian Premier Jay Weatherill insists wind farms were not to blame.

AEMO noted “the proportionally low amount of conventional generation dispatched in SA at the time of separation, and the subsequent low inertia, resulted in a higher [rate of change of frequency] than had been experienced during previous separation events”.

The operator has ordered two major gas-fired power stations to remain online to keep the grid secure.

More details are available here.