After load-shedding was suspended for the first time in five weeks this weekend, Eskom warned that it may return at short notice on Monday.

During the early hours of Monday morning, there were two electrical faults in quick succession in the high voltage yard at Kriel power station.

The fault, which appears to be related to the heavy mist, is under investigation, Eskom said.

The first fault caused units 1, 2 and 3 of the power station to trip, while the second fault tripped units 4 and 5. The incident removed more than 2 000 MW of generation capacity from the network.

While some generation units at other power stations are expected to return to service during the day, these will take time to load to full capacity.

"Should there be any further loss of generation capacity during the day, or some units fail to return to service as anticipated, load shedding may be required to be implemented at short notice," Eskom said.

Some 1 018 MW in electricity output is offline due to planned maintenance, while another 17 022 MW of capacity is unavailable due to breakdowns.