During 2016 a series of storms caused a widespread power outage in South Australia. As a result, a significant amount of work has been undertaken by AEMO to build a more secure grid. In 2017 AEMO released a review of the events which blacked out the state, a significant cause was the extreme weather that resulted in transmission lines being knocked over as well as some windfarms not meeting protection standards.
On November 12th a similar event occurred with a series of storms passing through South Australia causing the tripping of multiple transmission lines. Some transmission towers were damaged and fell over resulting in the South Australian grid being disconnected from the NEM. During this period, South Australia was powered by wind and solar for up to two thirds of its electricity demand with gas providing the difference.
The South Australian network has now been re-synchronised to the NEM and electricity is flowing between South Australia and the other states of the NEM as before.
During events like this AEMO invokes its power to manage system security, however this time it went a step further and restricted roof top solar PV to maintain a secure level of Distributed PV (DPV) generation. AEMO switched off as much rooftop PV installations as possible during the middle of the day, by curtailing the rooftop PV they were able to manage scheduled and semi scheduled generation assets to maintain system security.
System stability is a fine balance of the supply of electricity, the types of generators providing the electricity and the demand of electricity from end users. Part of the solution this time was to encourage end users to consume more electricity enabling a higher level of generation. Prior to the curtailment, South Australia was being supplied by over two thirds of it demand via renewable generation.
While high levels of renewable generation is good to keep electricity costs down, the savings can be eroded by high frequency control costs and the need for more expensive gas fired generation to fill the gap when the sun is not shining and the wind is not blowing.