South Africa is subjected to the deepest nationwide power cuts in months as the state-owned power company confronts generation capacity constraints and diesel shortages.
Eskom implemented so-called Stage 6 outages, taking 6,000 megawatts offline to prevent a total collapse of the grid, “due to the shortage of generating capacity and emergency reserves,” it said in a statement Friday.
The return of this level of electricity rationing — expected to last through Monday — is a step backwards for South Africa’s government, which has prioritized stabilizing the system.
Eskom last instituted Stage 6 blackouts in September. Warmer weather in the southern hemisphere typically results in less electricity demand.
South Africa’s rand extended losses after the announcement, weakening 0.6%. Eskom’s inability to meet demand and port and rail bottlenecks are limiting economic growth in Africa’s most industrialised economy.
Eskom’s open-cycle gas turbines intended for use during peak demand have been run for longer periods to offset breakdowns, and the diesel used to run them needs to be replenished, South African Electricity Minister Kgosientsho Ramokgopa said at a press conference with Eskom executives. “We’ve over-committed our reserves.”
Last week, the minister said South Africa will cap diesel for the auxiliary units at R30 billion for the current fiscal year.
Time is also needed to refill reservoirs with water used to power turbines at pumped-storage plants, another type of peaking unit.
Kusile, Eskom’s newest coal-fired plant, is expected to return to generating capacity in the coming weeks, while other repairs will be accelerated, Ramokgopa said.
The reason for stage 6 load-shedding
Ramokgopa revealed that Eskom implemented stage 6 load-shedding because it over-committed its emergency reserves.
He said the power utility has had to cut back on using open-cycle gas turbines (OCGTs) and pumped water storage schemes.
Eskom was forced to ramp up the use of its emergency reserves after a “cluster” of generation units broke down.
“On the back of that cluster of units that had gone out, what it meant is that we had to significantly engage our emergency reserves,” he said.
Curiously, he said the increase to Stage 6 load-shedding isn’t a result of unit breakdowns. “We have lost a few units, but those don’t explain the initiation of Stage 6,” said Ramokgopa.
“If you were to look at our numbers — the UCLF [Unplanned Capacity Loss Factor] — we are talking about 15,300MW. That’s not out of the norm.”
Ramokgopa said Eskom over-committed its emergency reserves and has had to cut back on its use of OCGTs and pumped storage.
“We don’t have the benefit of the 4,600MW that we would automatically draw from our emergency reserves,” he said. “As a result of that, it calls for the intensification of load-shedding.”
What the data says
While the minister claims that the UCLF is within normal levels, Eskom’s plant performance data tells a different story.
The data shows that unit breakdowns have increased in recent weeks. Before the implementation of Stage 6 load-shedding, Eskom maintained lower stages due to lower demand and reduced planned maintenance.
Recently, demand and planned maintenance have trended upwards. Eskom Group executive for generation Bheki Nxumalo said that demand is 1,500MW higher than expected.
“We have noticed that demand today compared to yesterday is continuously above by 1,500MW,” he said.
Nxumalo said one of the reasons for the higher demand could be ramped-up air conditioner use as a heatwave has hit much of the country.