Eskom regularly implements outages in Africa's most industrialised economy because of faults at its ailing coal fleet which has held back economic growth.
The outages increased from "Stage 2" to "Stage 4," requiring up to 4,000 megawatts (MW) to be shed from the national grid, until Friday 5 a.m. (0300 GMT). After that they will be scaled back to Stage 2 until Saturday at 5 a.m.
"Over the past 24 hours a unit each at Medupi, Kusile and Matla power stations tripped while a unit each at Lethabo and Arnot power stations were forced to shut down," Eskom said in a statement.
"This constrained the power system further requiring extensive use of emergency reserves."
Eskom said total breakdowns amounted to almost 15,000 MW, while over 5,000 MW was out on planned maintenance. The utility has a nominal capacity of around 46,000 MW and supplies over 90% of the country's electricity.
On Monday, Eskom said South Africa needed an extra 4,000 to 6,000 MW of generation capacity to eliminate the risk of scheduled power cuts.
Public Enterprises Minister Pravin Gordhan told a media briefing on Wednesday evening that he had met Eskom's board and management to discuss the power challenges, ahead of municipal elections on Monday.
Gordhan said he was assured by Eskom that the scheduled power cuts will not proceed into the weekend and next week.
"It's quite clear the electricity system in South Africa urgently requires more megawatts to be on the system. This is something that we have been talking about for the last two years," Gordhan said.
"It is now urgent that all those parties that are responsible ensure that we utilise gas or ensure that the right amount of private investment takes place (to introduce) more megawatts in the country."
(Reporting by Alexander Winning and Olivia Kumwenda-Mtambo; editing by David Evans and Aurora Ellis)
