SA has never experienced a national blackout and the likelihood is “extremely low”, according to Isabel Fick, Eskom’s system controls general manager.
Fick also allayed fears that delays in maintenance work at Koeberg, which may result in both 920MW generating units at the nuclear plant being offline simultaneously later this year, would increase the risk of a regional blackout in the Western Cape.
Both Koeberg units were out of commission for 48 hours in April and there was “quite a bit of stability in the Western Cape”, even without these units, she said.
Monique le Roux, a senior researcher at the Council for Scientific and Industrial Research with expertise in energy systems said their modelling shows the grid can operate stably without Koeberg — even under scenarios where there is a higher penetration of renewables on the grid.
“Obviously Koeberg does provide a lot of stability to the Western Cape grid which could be quite unstable if the renewable energy penetration increases [in the province]. But there are measures that can be put in place to compensate for that,” Le Roux said.
This could include, for example, the use of dispatchable generation from sources such as gas or batteries.
In the unlikely event that a national blackout does occur, Fick said Eskom has a response plan, though but it would take six to 14 days to restore the system.
During an information session on Wednesday organised by the government’s communication service, Fick and other energy professionals discussed the factors that could lead to a national blackout and Eskom’s ability to respond.
Jan de Kock, president of the SA Institute of Electrical Engineers, echoed Fick’s comments, saying that even during the current high winter demand, SA was “nowhere near a national blackout or grid collapse”.
Still, he did warn that “we often operate close to the edge”.
De Kock explained that a blackout usually occurs after a sequence of events, such as inherent system weaknesses and cascading failures, that can develop over the course of hours or even in minutes.
Typical triggers include natural disasters such as earthquakes and flooding, human error, network disturbances, and multiple, simultaneous plant breakdowns.
“Our network often faces threats, for that SA has “resilient barriers” in place to ensure that very few such events would lead to a blackout.
Some of the “positives” that reduce SA’s risk of a national blackout include having one central system operator instead of several, and having a grid code in place that addresses the problem of multiple trips.
“Eskom has extensive experience [managing a system under pressure] with load-shedding and operating with very small reserve margins,” de Kock said.
However, because SA has never experienced a national blackout and only a few regional blackouts, there is limited experience in restarting a system. “Eskom has done exercises to prepare for this, but [an exercise] can be a lot different from the real thing”, he said.
De Kock said few of Eskom’s power plants have black start capabilities that are needed to jump start the grid using, for example, an on-site standby generator. However, he added that some of the plants that do have the capability, such as Tutuka power station, are poor performers and prone to unit breakdowns.
Tutuka is one of Eskom’s worst performing plants. Earlier this year it was delivering just 17% of its installed capacity of 3,654MW.
To better prepare for the possibility of a national blackout SA should develop strategies to respond to emerging risks such as cyberthreats, he said.
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