Stage 4 load shedding will start at 14:00 on Friday, Eskom has announced.
Three units at the Kendal power station were taken offline and a unit each tripped at Tutuka and Matimba. The return to service of a unit each at Majuba and Lethabo have also been delayed.
Stage 4 will roll out on Friday afternoon until 05:00 on Saturday, and thereafter, Stage 2 will be implemented until 05:00 on Monday morning.
The conveyor belts supplying some units are currently not running due to a power fault, Eskom said earlier. There is also insufficient diesel available for emergency reserves.
Total breakdowns amount to 17 437 MW and planned maintenance is at 4 371 MW.
South Africa had a two-day break from load shedding, with rolling blackouts suspended on Wednesday morning.