Yesterday Eskom spokesperson Khulu Phasiwe said there were signs the power system could be constrained from late in the afternoon, making the risk of load shedding high.
The power utility had implemented stage 1 load shedding by 5pm yesterday.
He said several units had technical faults.
“Many of our substations are very old and therefore maintenance work has to be done on them frequently, while none of the newer ones are less than 20 years old,” Phasiwe said.
The oldest of the substations is Grootvlei, where the first unit was commissioned in 1969.
Others include Hendrina power station which became operational in the early 70s and Matimba and Matla, which were built in the early 1980s.
“We also had Medupi power station’s unit 6 which was taken offline sometime this week, but are expecting it to be brought back online sometime this weekend,” said Phasiwe.
He said synchronisation work has already been concluded at the unit in question, but engineers were still busy with optimisation work to ensure it will generate the power it is expected to.
The unit has been generating up to 800MW a day to the national grid since May. Asked when the unit would be fully operational, Phasiwe said the official handover of the unit to Eskom was likely to be either later this month or next month.