The credibility of South Australia's energy network was in the spotlight again on Wednesday night after it was revealed a computer glitch resulted in 60,000 extra households and businesses being unnecessarily plunged into darkness during last week's blackout.
A report from the Australian Energy Market Operator released on Wednesday afternoon found both lower than expected wind power and the failure of thermal generators to step in to stop a shortfall in supply led to the blackout in SA last Wednesday.
But the AEMO report revealed more than 300 megawatts was shed from the power network – resulting in 90,000 homes and businesses losing power – when it asked that only 100 megawatts (or about 30,000 homes and businesses) be removed to protect the state's power network, which was dealing with a heatwave.
SA Power Networks on Wednesday apologised for its software blunder in a further embarrassment for the state's power system, which is already under intense scrutiny after three major blackouts in the past five months.
The company said at 6.40pm SA time on that day, load shedding started using "an automated load-shedding software system".
Within 10 minutes SA Power Networks network controllers raised concerns that more load was being shed than the 86MW the load-shedding system was indicating. This meant three times more households and businesses had their power cut than was necessary."We have put in place steps to prevent a recurrence, while continuing detailed technical investigations into why the load-shedding software did not operate correctly," the company said.