The failure of wind farms in South Australia to deal with network faults on the state’s electricity network during last month’s destructive storms was greater than first thought, according to the latest update from the Australian Energy Market Operator.
But AEMO is also critical of two gas-fired power stations that failed to kick into to re-energise the electricity network when SA was cut off from the rest of the NEM and plunged into darkness on the afternoon of September 28.
An initial report from AEMO earlier this month found that six wind farms disconnected 315 megawatts from the grid once the storm hit after three long-distance transmission lines were blown over by strong winds.
But an update into the investigation released on Wednesday found nine of the 13 wind farms online at the time did not “ride through” – or continue normal operations – after the six voltage disturbances, resulting in a loss of 445 megawatts of generation – 130 megawatts more than originally thought.
This put increased pressure on the Heywood Interconnector with Victoria to deal with the shortfall in electricity supply in South Australia, which eventually “tripped” to protect the rest of the NEM, plunging SA into a “system black”.
“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 report found.
“Thermal generators remained connected up until the SA system disconnected from the remainder of the National Electricity Market.”
The latest findings is expected to provide further ammunition to critics of renewable energy who argue wind and solar do not provide the same energy security as synchronous generation like coal-fired or gas-fired generation.
Energy Minister Josh Frydenberg said he was concerned about energy security following SA’s head-long dive into renewable energy which now accounts for 40 per cent of the state’s energy supply.
But the AEMO report also highlights the failure of two gas-fired generators which were supposed to help provide System Restart Ancillary Services to re-energise SA’s power network during the state-wide blackout.
“The two contracted SRAS suppliers both experienced difficulties in providing system restart services due to two separate faults,” it found.
“Both facilities successfully tested their restart capacities earlier this year, so AEMO will further explore the nature of the faults experienced on 28 September 2016.
“AEMO will continue to investigate why SRAS suppliers did not perform as AEMO expected.”
The French owner of wind farms in South Australia said earlier this month the Hornsdale wind farm shut itself down in the seconds leading up to the South Australian blackout to protect itself.
The AEMO report found the transient reduction in output was spread across all wind farms online at the time, including those that did not suffer a sustained reduction in output.
The report found that while the configurations of the wind farms to disconnect from the grid due to transmission faults was standard for the model of turbine this information had not been passed on to AEMO during the NEM registration process prior to the wind farms commencing operations.
“The wind farm operators and the turbine manufacturers are working to propose improved ‘voltage ride-through’ settings for consideration by AEMO,” it said.
AEMO chief operating officer Mike Cleary said the wind farm operators and their suppliers had control over the “ride through” mechanisms on their wind turbines to protect them from damage.
He admitted AEMO – which runs the national gas and electricity market – did not know what these controls were. “That is true,” he said.
The AEMO report found SA network operator ElectraNet had restored most of the state’s power five hours after it had been disconnected from the NEM.
South Australian Treasurer Koutsantonis on Wednesday again defended SA’s pioneering approach
to renewables energy and said the second AEMO report showed the problems weren’t the result of being too reliant on wind energy or other renewables sources, but a “software glitch” by the wind operators.
He said wind farm operators needed to make sure software in their systems was more robust, and warned they couldn’t hide behind claims that software was proprietary information that couldn’t be made public.
“It wasn’t the intermittent nature of the generation that caused the system black. It was a software issue. So yeah, the software needs to be fixed up,” he told The Australian Financial Review on the sidelines of an Energy Users
Association of Australia forum in Adelaide.
Australian Energy Council chief executive Matthew Warren said the latest AEMO report reinforced the need to change the way the electricity grid is managed to deal with the influx of renewables.
“South Australia is a living experiment in how we manage high levels of renewables in modern electricity grids. It is hard to anticipate and test for real world situations like this until they occur,” Mr Warren said.
“While the blackout was caused by a cascading set of events from extreme storms on the day, the most important thing is that we learn from this experience and do everything we can to prevent it reoccurring in the future.”
Mr Frydenberg said SA’s recent blackout was a “wake-up call” which underlined the importance of energy security, saying multiple reviews would be looking at the issues of the resilience of wind and solar in the NEM.
“AEMO’s updated report confirms that the sequence of events of the blackout remains unchanged, starting with a storm damaging the transmission network,” he said.
“Importantly it was the settings within the majority of the wind farms which meant they could not ride through the voltage disturbance caused by the storm.”
Clean Energy Council Chief Executive Kane Thornton said the damage to more than 20 electricity pylons and three transmission lines during the once-in-50 year storm remained the main cause of the SA blackout.
“The reality is that South Australia’s electricity system went through one of the largest power system disturbances ever seen in the country at the end of last month,” Mr Thornton said.
“No power grid in the world is designed to manage the rapid consecutive collapse of three major transmission lines like the SA system sustained on 28 September.”
AEMO will provide a final report on the SA black-out to the Council of Australian Governments energy council in December. There is also a review headed by chief scientist Allan Finkel which will look at the integration of renewable energy into the NEM. With Simon Evans.
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