Johannesburg - Eskom on Wednesday outlined the reason for the implementation of load shedding on Wednesday, saying it was being done to "protect the power system from total collapse".
Earlier, the embattled power utility announced it would be implementing Stage 2 load shedding from 9am to 11pm due to a "shortage of capacity".
This about turn comes barely a month after it dismissed the DA's claims that there were plans to initiate load shedding soon.
The power utility in a statement confirmed that its electricity system has been severely constrained this week.
"As a result of the loss of additional generation, delays in the return to service of units that are on planned maintenance and limited diesel supply, it has become necessary to implement stage 2 rotational load shedding from 9am until 11pm in order to protect the power system from a total collapse.
"In the System Status Briefing of 4 September 2019 Eskom warned that in order to avoid load shedding, unplanned breakdowns needed to be contained at below 9 500MW. In the event generator breakdowns are experienced beyond 10 500MW there will be high usage of emergency resources (diesel and pumped storage generators), which may lead to load shedding if the supply constraints is sustained for a long duration.
"The severe supply constraint being experienced has come about due to high levels of unplanned breakdowns that have exceeded the 10 500MW limit. The supply constraint is caused by, among others, five generating units that are unavailable due to boiler tube leaks. In addition, a conveyor belt supplying Medupi power station with coal failed on Saturday 12 October resulting in low volumes of coal being supplied to the power station thus limiting the generating capability to approximately half the station output."
The utility further said: "Due to the shortage of generating capacity from coal fired generation, the pumped storage and OCGT generators have been used extensively since Saturday, 12 October which has led to a decline in the dam levels and diesel tank levels.
"We unreservedly apologise to South Africans for the negative impact this may have on them and want to assure the nation that we continue to work tirelessly to ensure security of energy supply.
Eskom urged citizens to check their load shedding schedules on the Eskom or municipal website.
"We will keep customers informed if there are any further changes to the power system," the utility said.