Can South Africa’s electricity grid COLLAPSE TOTALLY? – Total Eskom blackout chance “remote” despite high lo ad-shedding stages — Energy expert
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[This is a good technical article that answers questions about grid collapse. This is something I've been thinking of. I still think, in the years ahead this can happen. Jan]
The chances of a total power blackout occurring in South Africa are still remote, despite rising concern about the return to stage 6 load-shedding on Wednesday, 7 December 2022.
That is energy expert Chris Yelland’s view, given in a recent interview with Talk 702’s Bongani Bingwa.
A blackout happens when the power grid’s alternating current supply moves too high or too low. Eskom’s grid operates at a frequency of 50Hz — or 50 cycles per second.
Yelland said it was important to understand the stage of load-shedding was not necessarily a direct indication of the proximity to a national blackout.
“The fact that we have a particular stage of load-shedding for some hours or days actually indicates that supply and demand have been brought back into balance by this load-shedding, which will avert any possibility of a national blackout,” Yelland said.
Yelland said the system’s frequency and the frequency’s rate of change — and not the load-shedding stage — indicated the likelihood of a blackout.
“Stage 6 load-shedding has brought the frequency back up to where it should be. It is doing its job,” Yelland stated.
“It is when the frequency is dropping and not returning to 50Hz that you can say if that situation persists, then a national blackout may occur.”
He added that Eskom still had further “levers to pull” to bring the supply and demand back into balance under severe circumstances — including automatic load adjustment.
“At the moment, what we are seeing is manual rotating load-shedding,” Yelland explained.
“But there is a whole series of automated under-frequency load-shedding, both on a voluntary basis by customers and on an involuntary basis where Eskom’s load-shedding devices start kicking in automatically, and these respond very quickly.”
Yelland previously explained that a long period of operating at too high or too low a frequency would cause power distribution equipment to become overloaded.
In such a case, the same safety features designed to protect the hardware against catastrophic failure would cause a cascading trip-out.
When demand exceeds supply, generators, transformers, cables, and switch gears on the distribution network will become overloaded, causing trips along the distribution line.
That would place even more strain on components in the grid that are still on, causing further trips unless demand is reduced.
With an aerial view of the country at night, Yelland said one would see these cascading trip-outs spread as a wave of darkness sweeping across South Africa.
Another energy analyst, Ted Blom, previously warned a blackout could also happen if Eskom’s national control centre operators took their eye off the ball and didn’t implement the necessary load-shedding to keep supply and demand in balance.
Blom said there were examples of this occurring in countries like the USA, India, and Pakistan.
Eskom CEO André De Ruyter previously said that it would take a week or longer to get the grid back online after a total blackout, which could come at a disastrous cost to the economy.
Yelland and Blom have estimated it would take two to three weeks.
Grid restoration would be done through a “black start” process, where smaller generators at power stations gradually bring back larger generators and return the grid to its maximum capacity over several days.
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