Total grid collapse highly unlikely, say experts

Independent energy specialists say load-shedding is an essential part of avoiding the ‘extraordinary’ convergence of events that could spark disaster

14 May 2023 - 00:00

Hein Vosloo, a former senior manager in Eskom’s transmission department, said a complete collapse was “almost impossible” but could happen “under a set of extraordinary circumstances”. File photo.
Image: ESA ALEXANDER/SUNDAY TIMES

Despite rising fears that a total grid collapse could be imminent, a range of experts dismiss it as a remote possibility that would require highly improbable circumstances such as the simultaneous failure of all South Africa’s power sources.

Hein Vosloo, a former senior manager in Eskom’s transmission department, said a complete collapse was “almost impossible” but could happen “under a set of extraordinary circumstances”. 

“A complete collapse is possible if we lose several power lines at once, like what happened in the US in 2003,” he said.

“Either that, or if all our power stations go down simultaneously and we are left with no generation capacity.

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“That means the diesel power stations in the Cape fail, as well as the hydro supply from Cahora Bassa in Mozambique and both Koeberg units. The dams at our pump stations must be empty.

“If this perfect storm happens we will have a blackout and repairing it [quickly] would be virtually impossible because we won’t have electricity to get the system up and running again. That can cause weeks of blackout,” Vosloo said.

Independent energy expert Lungile Mashele concurred. 

“Our transmission maintenance is above 95%. You can also look at the active role the Eskom system generator plays in managing the grid. As long as we have load-shedding we won’t collapse,” Mashele said.

“It is important that we use tech that is flexible and despatchable — like gas and diesel — to fill the gaps.” 

North West University professor Jan de Kock, who is president of the South African Institute of Electrical Engineers, said the closest South Africa had come to a grid collapse was December 4 1974, when 24 generating units broke down.

“About 45% of the national grid lost power but it was restored within six hours,” De Kock said.

A collapse could only be precipitated by  an extraordinary sequence of events,  he said. 

Even if we don’t expect a national collapse of the grid I would still urge citizens to have backup plans in place

Fanele Mondi, CEO of the Energy Intensive Users Group

“There are on average six units at every power station. We would have to lose effectively eight units of at least 600MW each at the same time or in a rapid succession.” 

But even if this happened, it would not necessarily cause a total grid collapse. 

“A lot of technical and system improvements have been made since 1974. There have been several occasions when we had multiple units failing but the grid survived all of them,” De Kock said.  

The general manager of an Eskom power station, who did not want to be named, said: “The golden figure in safeguarding our national grid is the 50Hz frequency it is run on. As long as Eskom can maintain that frequency our grid will not fail.”

This source said the Eskom system was built to ensure the frequency did not drop to a critical level, which De Kock said would be anything below 47.5Hz.

“Should a serious problem arise, like let’s say an airplane falling on one of our big power stations or a critical node, the system will automatically isolate the affected units,” the Eskom manager said.

“That is called ‘islanding’. This ensures that an issue in one power station will not spread and affect the rest of the grid. I can’t say a total collapse of the grid is impossible, but it is highly unlikely.”  

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He said if a power station went down, it would  take “anything from one to six hours” to restore to service.  

“Should the entire Johannesburg go down, it should take four to 12 hours to restore if the network is not damaged, for example by a plane crash or fire, et cetera.” 

Fanele Mondi, CEO of the Energy Intensive Users Group, said that while a national blackout was not likely, it “is possible on any system in the world”.

“Just look at the UK where a blackout in 2022 affected 1.4-million customers. They have a very good system, yet it happened to them. To this you can add Bangladesh, where 150-million customers were affected last year, and Pakistan, where 200-million customers were affected the year before.

“In 2021, 4-million US customers were affected when it happened to them,” Mondi said.

“Our challenge is still generation, but that does not necessarily mean we are heading for a blackout. In most cases blackouts were not the result of generation failure, but of weather and transmission faults.” 

Mondi expressed confidence in Eskom’s ability to avoid total collapse.

“Our system operator and team are doing incredible work in managing the grid. [But] even if we don’t expect a national collapse of the grid I would still urge citizens to have backup plans in place.”

History of Eskom's largest unit failures.
Image: Ruby-Gay Martin

Hartmut Winkler, a professor of physics at the University of Johannesburg, said the grid would collapse if Eskom tried to distribute more electricity than was available — so load-shedding was a blessing. 

“If we stopped load-shedding completely now and switched everything on, we would have a collapse immediately.”  

Eskom spokesperson Daphne Mokwena defined a grid collapse as the “complete national blackout of the grid, where the entire network is de-energised and all generators are disconnected”.

“Depending on how a blackout occurs, some generators may ‘island’ or all generators may run down to a standstill condition,” she said. 

“To restart the grid from generation units that have islanded is significantly faster than restoring the grid where no generators are running. In either case, these events follow after a national blackout or complete grid collapse.”

Nedbank chief economist Nicky Weimar, who told a webinar in March that South Africa had narrowly dodged a blackout the previous month, said the system was vulnerable.

“Now that Eskom has higher stages of load-shedding, it seems a lot less likely that you will have a blackout.  

“What creates the threat of a blackout is that you have a very poor generational capacity, which is old with unexpected breakdowns, but you are going into winter, which has high demand.”

She said Nedbank has been running scenarios of total grid failure.

“I think all companies have been asked to prepare for a worst-case scenario. It is part of your operational risk management in any case. If anything were to go wrong you need to know what sequence of events will you follow to make sure all your customers, staff and systems are protected.”

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MTN South Africa spokesperson Jacqui O’Sullivan said the company would continue to accelerate its resilience plan, which includes the rollout of additional batteries, generators and enhanced security features.  

“MTN believes the likelihood of a total grid collapse remains very low, but in line with good risk management principles, detailed planning is under way to consider MTN actions in a number of different power scenarios.” 

The South African Reserve Bank said the fact that it was drafting plans for dealing with a total grid collapse was “not an indication of how likely or not it regards this scenario to be”.

“In a scenario of a grid shutdown … the plans revolve around ways in which critical payment and transaction services could be provided for as long as possible, and, where they cannot, for the process to be managed in an orderly way to minimise the longer-term impact on the financial system,” said spokesperson Thoraya Pandy.