The Australian Energy Market Operator (AEMO) updated its findings on South Australia’s state-wide blackout on September 28, saying that five system faults occurred within 88 seconds, causing six voltage disturbances.
Amid the problems, nine of 13 wind farms online at the time “did not ride through the six voltage disturbances, resulting in a loss of 445 MW of generation”. Operators have since adjusted their settings to help them ride through a higher number of disturbances, the AEMO says.
“Preliminary discussions with wind farm operators suggest this inability to ride through all disturbances was due to ‘voltage ride-through’ settings set to disconnect or reduce turbine output when between three to six disturbances are detected within a defined time period,” the AEMO’s report says.
A ride-through is the capability of generators to stay connected through gaps caused by power dips. After the wind power dropped out, thermal generators remained connected until the SA system disconnected from the remainder of the national grid network.
“The Heywood Interconnector remained connected up until the sudden increase in electricity flow resulting from the loss of generation caused the automatic protection mechanism to disconnect the lines,” the report says.
The cavalcade of problems continued according to the AEMO, including difficulties in providing system restart services due to two separate faults. Further investigation why that happened is under way because testing earlier in the year show a restart should have worked.
AEMO is planning to provide a update ahead of December’s COAG Energy Council meeting, while the full report and recommendations will take up to six months to finalise.
In response to the latest analysis, Clean Energy Council CEO Kane Thornton says the report shows a blackout was inevitable no matter what generation was running at the time.
“No evidence has been provided to show that the system would have remained up and running if wind farms in the state had not tripped off to protect themselves in an unsafe electrical environment,” he said.
“The reality is that South Australia’s electricity system went through one of the largest power system disturbances ever seen in the country.
“On the current information available, the damage to the transmission system was the main cause of the event. No power grid in the world is designed to manage the rapid consecutive collapse of three major transmission lines.
Thornton said there was still “a lot to learn” from the incident, “from the operation of the interconnector to the robustness of the transmission network, the re-start procedures, the planning prior to the extreme weather and the operation of power generators”.
The latest AEMO report is here.
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