The power cuts will be at the "Stage 2" level, which requires up to 2,000 megawatts to be shed from the national grid, but Eskom said in a statement that they could escalate.

Among the faults cited by Eskom, a unit at the Tutuka plant tripped, three Kendal units were taken off and a fourth was also expected to be shut down.

Power outages are a major constraint on economic growth in Africa's most industrialised nation.

(Reporting by Alexander Winning; Editing by Emma Rumney)