Eskom has announced that it is jumping to Stage 4 load shedding at noon on Wednesday, and this will continue until 05:00 on Friday.
Stage 2 load shedding will then be in effect until 05:00 on Saturday, as announced by the utility earlier in the week.
"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. This constrained the power system further requiring extensive use of emergency reserves and therefore, hampering the recovery of these reserves," Eskom said in a statement.
"Some generating units have returned to service and we anticipate another two units to return to service during the day. In addition, Koeberg Unit 1 is expected to return to service today and begin ramping up to full output within 48 hours."
It said the implementation of Stage 4 is "no cause for alarm as the power system remains to be effectively controlled".
Total breakdowns currently amount to 14 957 MW while planned maintenance is 5 301 MW of capacity.
On Monday night, two units at the Kusile and Matimba power stations also tripped, adding to the strain on Eskom's capacity.