Brown said this following the power utility's decision to implement load shedding over the past few days due to a shortage in generating capacity.
Briefing journalists in Cape Town on Wednesday, Brown apologised to the public for the inconvenience caused by load shedding.
"This year, Eskom has been following its preventative maintenance schedules to the aging plants so that the recovery to sustainable and reliable power generation is expedited.
"This will understandably place strain on the system over the short term as... additional plant failures, as experienced over the past few days, which took us into stage two and stage three load shedding, might occur.
"I once again appeal to all citizens to help us reduce demand by making electricity reductions [at home and at work]," she said.
On Monday, Eskom implemented stage two load shedding and load curtailment from 4pm until 10pm due to a shortage of generating capacity because several units were out of service due to planned and unplanned outages. Yesterday, it moved to stage three.
On Tuesday, the situation worsened at 6pm when stage three had to be implemented due to a further shortage of generation capacity as additional units had to be taken out of service for unplanned maintenance caused by technical faults, Brown said.
"Load shedding at stage three shows the seriousness of the constraints that we face but it is in no way an indication that we are close to a black-out," she said.
While she could not give further details that touched on operational occurrences at various plants, Brown said Eskom's acting chairperson Dr Ben Ngubane has provided her with a detailed report on what happened during the last week.
She said about 9,500MW of power was lost when some units went off-line.
Load shedding will be with the country for the next two years, Brown said.
"The loss of a number of generating units early in the week reduced the available capacity to meet the demand on Monday.
"It is expected that the situation would continue throughout winter when consumption is higher as the constraints on the grid mean that planned, controlled, and rotational load shedding and load curtailment, are introduced to protect the power system."
Brown said, meanwhile, that the electricity war room, which was set up in December to address several energy challenges, has made several successes.
This includes, amongst others:
• Medupi Power Station reaching its milestone by delivering power to the grid on 2 March 2015 from its unit six generator. Once on-line, the unit will bring 800MW to the grid;
• Restoring the Majuba Power Station is underway and 1,200MW has been recovered as part of the solution;
• Eskom's maintenance strategy and its execution are receiving focused attention from the war room to ensure that it delivers improvements required in plant availability and performance. Thirty experienced senior managers have been deployed to power stations in this regard;
• A R4bn loan was recently secured to scale up Eskom's renewable energy generation capacity. Eskom will build the Kiwano Solar thermal power station in the Northern Cape and the Ingula Pumped Storage Scheme in KwaZulu-Natal, which will add 100MW and 1,332MW respectively to the national grid;
• The completion of the Sere Wind Farm in Vredendal in the Western Cape and KaXu Solar One Power Plant in Pofadder in the Northern Cape have together added 200MW to the national grid; and
• The co-generation contracts were successfully renewed at the end of March, ensuring 800MW to the grid.
