Stage two rolling power cuts will be implemented on Thursday morning, power utility Eskom said.
The power outages would be from 8am until 11pm due to a shortage of generation capacity, the Eskom media desk tweeted on its official account.
On Wednesday, the power utility said unit 3 at Majuba power station had an ash conveyer belt which was stuck and at Duvha, unit 2 tripped on Tuesday night due to a technical fault.
Work continued at Koeberg which experienced a fault on Sunday.
On Monday, Eskom said the power grid was under pressure after one of Koeberg's 900MW units was taken out of service because of a technical fault.
"The unit is expected to be at full capacity by the end of the week. The same unit is due for planned outage on 9 February 2015 and will be returned to service again in May," the power utility said at the time.
Eskom said it would continue to provide regular updates on the status of the power system.
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