Eskom appears to be on the verge of implementing Stage 7 load-shedding, with the power utility’s recent peak supply and demand figures painting a bleak picture.
Its peak demand figures for Monday and Tuesday, 8 and 9 May 2023, show that it ran 19 open-cycle gas turbines (OCGTs) and implemented Stage 6 load-shedding and Stage 4 load-curtailment.
Stage 4 is the highest level of load-curtailment at the power utility’s disposal, based on previous feedback to questions about the demand reduction mechanism.
If Eskom were to lose more generation capacity to breakdowns or demand increases further, the only lever it would have left to avoid grid collapse would be to increase load-shedding.
Load-curtailment is a mechanism Eskom uses to reduce demand from energy-intensive users in South Africa, like mines and smelters.
In return for their participation, these customers are compensated financially by Eskom and can be exempted from national stage 1 and stage 2 load-shedding.
However, with the maximum level of load-curtailment already in effect, Eskom may have little choice but to implement higher stages of load-shedding if further generation losses occur, with the next step up being Stage 7.
Evening demand has peaked at around 18:00 in the evenings, according to Eskom’s latest demand figures. It also tracks demand trends on its PowerAlert page.
The chart below shows how South Africa’s electricity demand fluctuates during the day and night.
Throughout the day on Wednesday, the PowerAlert page stated: “The national power system is critical. Please SWITCH OFF.”
MyBroadband asked Eskom for comment on the matter, but it had not responded by the time of publication.
Eskom has been under fire for allegedly lying about the stage of load-shedding implemented. However, this is because it cannot report load-curtailment statistics separately from load-shedding figures.
For example, Eskom’s peak demand stats for Monday, 8 May, show 6,376MW of load-shedding. The common understanding is that 1.000MW equates to one stage of load-shedding.
Therefore, energy experts and South Africans assumed that Eskom secretly implemented Stage 7 load-shedding when the figure exceeded 6,000MW.
However, Eskom has now added a short explanation for exceeding 6,000MW in brackets after the figure, stating that the total load-shedding figure includes load-curtailment.
Evening Peak 09/05/2023 (18:22)
Eskom Availability: 25 701 MW.
Load Shedding: 6555 MW (LS stage6 and load curtailment stage 4)
Total demand: 33 190 MW
———————————
-Number of OCGT’s Utilised: 19
-IPP Availability (Dispatchable): 1 014 MW
-Renewable Gen: 777 MW
-RES:Wind 373…— Eskom Hld SOC Ltd (@Eskom_SA) May 10, 2023
While the obvious solution would be to report load-shedding and load-curtailment figures separately to avoid confusion, Eskom says this isn’t possible.
It told MyBroadband that doing so would be complex because the evening peak figures it reports are mainly from historical demand data and not real-time figures.
“The measurement of actual individual demand reduction is challenging — even more so if it is required to split into shedding and curtailment,” Eskom said.
“However, at a national level, Eskom uses statistical methods to derive how much total demand was reduced from the power system. Therefore, the two categories of load reduction are reported in totality.”
Load-curtailment explained
Load-curtailment, while achieving the same goal of reducing demand on the national grid, differs significantly from load-shedding.
During load-shedding, Eskom’s System Operator sets an amount of megawatts that must be shed to ensure the power utility can’t meet peak demand.
However, with load-curtailment, customers must reduce their demand on a proportional basis, according to the stage implemented as follows:
- Stage 1 and Stage 2 load curtailment (combined) — 10%
- Stage 3 load curtailment — 15%
- Stage 4 load curtailment — 20%
Eskom said its key industrial customers have been on load-curtailment since the mechanism’s inception.
“In the recent past, some of the smaller customers have requested curtailment,” Eskom said.
“Customers who meet the requirements of curtailment and can be isolated on the network, have been allowed to curtail their load.”
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