CAPE TOWN, Nov. 5 (Xinhua) -- South Africa's electricity system remains severely constrained, which might lead to more load shedding at short notice, electricity utility Eskom warned on Tuesday.

"We remind customers that any unexpected shift, such as additional unplanned breakdowns or the unavailability of diesel or pumped water storage reserves, could result in load shedding at short notice," the state-run parastatal said. 

Since the past weekend, plant performance has deteriorated with unplanned breakdowns reaching a high of 12,500 MW before reducing to approximately 11,500 MW as at 10:00 Tuesday morning, said Eskom which provides more than 95 percent of electricity consumed in the country.

Eskom is currently using emergency resources, being diesel and pumped water storage to keep the lights on, the utility said.

With the expected return to service of several units today and tomorrow, and with current diesel reserves, the probability of load shedding remains low for the week, Eskom said.

But the system remains constrained until at least Thursday, it said.

Unplanned breakdowns above 9,500 MW require the use of emergency resources at a high rate (diesel and pumped water storage generators) and they increase the probability of load shedding if the supply constraints are sustained for a long duration, said Eskom.

"Our summer maintenance program is underway, and technical teams are working tirelessly to keep to schedule and bring back generating units from planned and unplanned maintenance," it said. 

Embattled Eskom implemented rolling blackouts for four days running last month, dealing a heavy blow to the economy.

For years, Eskom often resorts to load shedding to avoid a total collapse of the national grid. The utility blamed the breakdown of several power generating units for the latest rolling blackouts. But poor management and alleged corruption are believed to be behind constant load shedding.

Last week, international rating agency Moody's downgraded South Africa's credit rating outlook from "stable" to "negative," citing poorly performing state-owned enterprises (SOEs), particularly Eskom, as one of the main factors that led to the downgrade.

Acute financial stress for Eskom and other SOEs continues to require sizeable ongoing support from the government, Moody's said in a statement. 

(Photo: VCG)