How Eskom is avoiding Stage 7 load-shedding
Eskom has managed to avoid Stage 7 load-shedding in recent days and weeks by implementing Stage 4 load-curtailment, Stage 6 power cuts, and burning diesel in 19 open-cycle gas turbines (OCGTs).
Several experts have said that the state-owned power utility is simply avoiding officially announcing higher stages of load-shedding by taking load off the grid in other ways.
However, the power utility told MyBroadband that it uses load-shedding and load-curtailment to ensure that emergency reserves — such as diesel and pumped water storage — are never compromised.
“The System Operator ensures that there are reserves available at all times to respond immediately to unforeseen events such as a generator trip,” it said.
“These reserves are never compromised, and the stages of load-shedding and load-curtailment are implemented to ensure these reserves are maintained.”
The power utility also has automatic protection schemes to ensure the grid’s integrity.
“In the event that a sudden trip of multiple generators occurs, beyond the reserve capability, there are automatic protection schemes in place to automatically reduce demand and normalise the power system,” Eskom said.
“This happens in less than 1 second.”
It confirmed that a new national standards document proposes providing load-curtailment stages higher than the current maximum of Stage 4.
“Stage 4 load curtailment is the highest stage of curtailment currently described in NRS048-9 Revision 2,” Eskom said.
However, the power utility explained that NRS048-9 Revision 3, which proposes higher stages of load-curtailment, is currently in draft for comment.
“Although there are some practical limitations on industrial plants,” it added.
Eskom peak evening demand trends. Source: poweralert.co.za
“Beyond Stage 4 load curtailment, the System Operator may instruct industrial customers to reduce to essential loads,” Eskom continued.
“This means the industrial customer must reduce all electricity consumption, apart from that which is required to make the plant safe.”
“Different industrial processes have different essential load requirements, which are declared upfront to the network provider and the regulator,” it added.
Load-curtailment reduces demand from the country’s energy-intensive users who can’t turn their power off entirely.
It is unclear how higher stages of the mechanism will impact these customers, which include the likes of mines and smelters.
Eskom has recently implemented Stage 6 load-shedding and Stage 4 load-curtailment, in addition to burning diesel in 19 OCGTs to meet evening peak demand.
With Stage 4 load-curtailment being the maximum level under the NRS048-9 Revision 2, this prompted concerns that South Africa was on the brink of Stage 7 load-shedding.
The power utility tracks evening peak demand trends on its PowerAlert page. Throughout the day on Wednesday, the page stated: “The national power system is critical. Please SWITCH OFF.”
The message was still being displayed on Thursday.
If Eskom were to lose more generation capacity to breakdowns or if demand were to increase further, the only option to avoid grid collapse would be to implement higher stages of load-shedding, with the next step up being Stage 7.
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