In this updated report, it is now known that five system faults occurred within a period of 88 seconds on 28 September 2016, leading to six voltage disturbances.
Data now shows that nine of the 13 wind farms online at the time of the event did not ride through the six voltage disturbances, resulting in a loss of 445 MW of generation. 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.
Thermal generators remained connected up until the SA system disconnected from the remainder of the National Electricity Market (NEM). 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 two contracted SRAS suppliers both experienced difficulties in providing system restart services due to two separate faults. 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.
Restoration of electricity load was able to commence within three hours of the Black System event, with all load that could be restored (approximately 80-90%) being restored within a further five hours. Following the construction of temporary towers, and the restoration of three of the four damaged transmission lines, ElectraNet was able to meet all power requirements in SA from late evening on 12 October 2016.
AEMO is continuing to consult with wind farm operators and wind turbine manufacturers to better understand the impact on the power system of their ride through settings. Several wind farms have already implemented revised settings allowing them to ride through a higher number of disturbances.
AEMO returned the SA spot market to normal operation at 23:30 (AEDT) on 11 October 2016, following the formal notification that the Ministerial direction to suspend the market had been revoked.
AEMO will present a further update ahead of the December COAG Energy Council meeting, and anticipates that a detailed report on the Black System event in SA, including final recommendations, will take up to six months to complete.
AEMO acknowledges and appreciates the significant work done by generators, network service providers and others to promptly provide the data used in its analysis to date.