He said Eskom would assess the situation during the course of the day and update consumers accordingly.

In addition to the problems at the Medupi Power Station, five electricity generating units are unavailable due to boiler tube leaks. 

Eskom also blamed outages on delays in the return to service of units that were on planned maintenance and said it is struggling with a limited diesel supply.

Oberholzer said the structural damage at Medupi, which would take until the end of the month to repair, had reduced Medupi's output by a third.

"At this stage, we simply do not know what has happened. We do not believe that it is sabotage or old age as the power station and the belts are relatively new," Oberholzer told TimesLive.

"The mechanical teams will have to determine exactly what happened. The problems look as though they were at the pulley systems which saw the belts wrap around the pulleys."

South Africa last experienced load-shedding in March this year. 

An Eskom board member warned recently that the power utility's generation fleet was last month as low as 69%, which should be as high as 80%.

It had been predicted that the country would be vulnerable to load-shedding from the end of August, when Eskom speeded up its plant maintenance programme.

Eskom board member Nelisiwe Magubane cautioned that an acceleration in economic growth in South Africa could trigger power cuts.

Experts believed that Eskom had succeeded in avoiding load-shedding for a couple of months due to a weak economy and that to manage the electricity supply efficiently, it had to ensure its plants are in good shape, regularly maintained and performing well.

Cape Times