Why Eskom is back to Stage 6 power cuts
The implementation of Stage 6 load-shedding on Friday, 24 November 2023, is because Eskom over-committed its emergency reserves.
According to electricity minister Kgosientsho Ramokgopa, the power utility has had to cut back on using open-cycle gas turbines (OCGTs) and pumped water storage schemes.
Ramokgopa said 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 during a media briefing on Friday, 24 November.
The electricity minister 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 [Unplannced Capacity Loss Factor] — we are talking about 15,300MW.”
“That’s not out of the norm. In relation to the winter plan, we should not be, especially on a day like Friday when we are expecting that demand is going to taper down, we don’t expect the initiation of intensified stages of load-shedding,” he added.
Ramokgopa said Eskom over-committed its emergency reserves and has had to cut back on its use of OCGTs and pumped storage.
“For purposes of protecting the grid, we need to ensure that we continue to protect the reserves, so we are not going to engage them at a heightened intensity, and as a result, 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.”
However, 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, with Eskom Group executive for generation Bheki Nxumalo saying during the Friday briefing 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 airconditioner use as a heatwave has hit much of the country.
Independent energy analyst Pieter Jordaan told BusinessTech that Eskom’s OCGT usage for the last week has far exceeded the 6% mark allowed for by the National Energy Regulator of South Africa (Nersa).
“Eskom’s OCGT utilisation rate for Week 46 was 40%, and on Sunday, it was 63%,” he said.
“Most of Sunday’s OCGT generation was used to replenish pumped storage, adding a 33% premium to the near R7 per kWh cost.”
“At these rates, the utility will run out of diesel supplies and may be forced to ramp up load-shedding, should the high breakdown levels (33.6% for Week 46) persist,” Jordaan added.
According to Eskom’s OCGT usage data, the state-owned power utility ramped up its use of diesel-burning generators from the Nersa-approved figure of 1,268GWh in July 2023 to over 2,500GWh in October 2023.
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