Eskom had to jump to Stage 4 load-shedding on Tuesday morning after a coal conveyor belt broke at Kendal, leading to cascading problems and the failure of three units at the power station. 

"In the early hours of this morning a conveyor belt feeding coal into Kendal Power Station failed. To conserve coal, the power output of the generators was reduced, but this required fuel oil to be used to sustain the boiler combustion," Eskom said in a statement. 

"Subsequently, the fuel oil plant supplying the units experienced a failure and shut down. This resulted in the trip of the three generating units. The Kendal units are anticipated to return to service by the weekend." 

Before this a generating unit each at Arnot and Medupi power stations had been taken offline for emergency repairs.

Eskom said there has been "intense" use of its pumped storage schemes and open cycle gas turbines to fill the generation gap due to the breakdowns. 

"While some generation units are anticipated to return to service over the next 24 hours, it is necessary to increase the load shedding to conserve the emergency reserves." 

Eskom said that 5 446 MW is out on planned maintenance, while another 16 985 MW of capacity is unavailable due to breakdowns.

Stage 4 started at 10:00 on Tuesday and is expected to last until 05:00 on Thursday morning. After that it will be lowered to Stage 2 until midnight on Friday.