I don't know what the root cause of this event was: CS Energy hasn't finished its investigation yet. Regardless of what the actual root cause was though, I think this looks a lot like what a network-launched attack on infrastructure would look like.
Three things that particularly stand out in this regard: the local SCADA for Callide C4 reporting to the operators that the unit was still exporting 278MW when in reality it was motoring, absorbing 50MW, for over half an hour; the generator CB for Callide C4 failing to operate; and the local protection at Calvale substation failing to operate for apparently unknown reasons - all lines into it tripped at the remote ends only.
Note that the operators did not regain control of Callide C4 - after absorbing considerable energy for considerable time, it tore itself apart.
Three things that particularly stand out in this regard: the local SCADA for Callide C4 reporting to the operators that the unit was still exporting 278MW when in reality it was motoring, absorbing 50MW, for over half an hour; the generator CB for Callide C4 failing to operate; and the local protection at Calvale substation failing to operate for apparently unknown reasons - all lines into it tripped at the remote ends only.
Note that the operators did not regain control of Callide C4 - after absorbing considerable energy for considerable time, it tore itself apart.